Bridge Maintenance, Safety Management, Health Monitoring and Informatics - IABMAS '08: Proceedings of the Fourth International IABMAS Conference, Seoul, Korea, July 13-17 2008

BRIDGE MAINTENANCE, SAFETY, MANAGEMENT, HEALTH MONITORING AND INFORMATICS

PROCEEDINGS OF THE FOURTH INTERNATIONAL CONFERENCE ON BRIDGE MAINTENANCE, SAFETY AND MANAGEMENT, SEOUL, KOREA, 13–17 JULY 2008

Bridge Maintenance, Safety, Management, Health Monitoring and Informatics

Edited by

Hyun-Moo Koh Seoul National University, Seoul, Korea

Dan M. Frangopol Lehigh University, Bethlehem, PA, USA

CRC Press/Balkema is an imprint of the Taylor & Francis Group, an informa business © 2008 Taylor & Francis Group, London, UK Typeset by Charon Tec Ltd (A Macmillan Company), Chennai, India Printed and bound in Great Britain by Antony Rowe (A CPI-group Company), Chippenham, Wiltshire All rights reserved. No part of this publication or the information contained herein may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, by photocopying, recording or otherwise, without written prior permission from the publishers. Although all care is taken to ensure integrity and the quality of this publication and the information herein, no responsibility is assumed by the publishers nor the author for any damage to the property or persons as a result of operation or use of this publication and/or the information contained herein. Published by:

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ISBN 13: 978-0-415-46844-2

Bridge Maintenance, Safety, Management, Health Monitoring and Informatics – Koh & Frangopol (eds) © 2008 Taylor & Francis Group, London, ISBN 978-0-415-46844-2

Table of Contents

Preface

XXXV

Conference organization

XXXVII

T. Y. Lin Lecture Fatigue of steel bridge infrastructure J.W. Fisher & S. Roy

3

Keynote Lectures Managing seismic performance of highway bridges – Evolution in experimental research M. Saiidi

13

Cost-effective and durable cable-stayed bridges H. Svensson

17

A new concept of orthotropic steel bridge deck M.-C. Tang

25

Health monitoring of structures & related education and training needs of civil engineers A.A. Mufti & J.P. Newhook

33

Practical implementation of probability based assessment methods for bridges I. Enevoldsen

41

Bridge monitoring in Japan: The needs and strategies Y. Fujino & D.M. Siringoringo

49

Bridging capacity innovations on cable-supported bridges Y.J. Ge & H.F. Xiang

53

Overcoming technological challenges to create new values for bridges S.P. Chang

63

Technical Contributions Advanced and high performance materials Durability of bridges made of advanced composite materials J.R. Correia, F.A. Branco, J.G. Ferreira, S. Cabral-Fonseca, M.I. Eusébio & M.P. Rodrigues V

83

Analytical study on the performance of reinforced high-strength concrete bridge columns D.J. Seong, H.M. Lee, H.M. Shin, J.H. Choi & M.S. Oh

85

Use of steel fibre concrete to eliminate shear reinforcement in pretensioned concrete beams P. De Pauw, L. Taerwe, N. Van den Buverie & W. Moerman

87

Durability of Structural Composite Lumber in bridge applications N. Yazdani, E.C. Johnson & S. Duwadi

88

Development of Self-Consolidating Concrete for bridge construction and repairs P. Paczkowski, A.S. Nowak, G. Morcous & M. Kaszynska

89

On the use of duplex stainless steels in bridge construction O. Hechler & P. Collin

90

Self-consolidating lightweight concrete – Excellent material for bridge applications M. Kaszynska

91

Assessment and control of bridge vibrations Detection of bridge damages by recognition of non-linear dynamic effects H. Wenzel Experimental dynamic analysis of steel concrete composite railway bridges: The Sesia viaduct on the high speed line Turin-Milan G. Chellini, L. Nardini, W. Salvatore, G. De Roeck, K. Liu, E. Reynders, B. Peeters, M. Tisalvi & G. Sorrentino

95

97

Excitation of pedestrian structures during marathon events C. Sahnaci & M. Kasperski

98

A novel active mass damper for vibration control of bridges U. Starossek & J. Scheller

99

Analysis of fuzzy active control for traffic-induced vibration of highway girder bridge M. Kawatani, Y. Nomura, C.-W. Kim & Y. Otsubo Sensitivity-based optimal design of damper connecting system for vibration control of parallel bridges under wind excitations D.-S. Kim, S.-Y. Ok, K.-S. Park, H.-M. Koh & C.-Y. Choi

100

103

Bridge 200 toward durable bridge Research project “Bridge 200” B.S. Kim, S.Y. Kim, K. Cho, J.R. Cho & S.T. Kim

107

Development of FRP bridge decks in Korea K.-T. Park, Y.-H. Lee, J. Jeong & Y.-K. Hwang

108

Development of FRP-concrete composite bridge deck system S.Y. Park, K. Cho, J.R. Cho, S.T. Kim & B.S. Kim

109

Development of Ultra High Performance Cementitious Composites (UHPCC) in Korea S.W. Kim, J.J. Park, S.T. Kang, G.S. Ryo & K.T. Koh

110

VI

Flexural strengthening of RC structures with externally unbonded prestressed CFRP plates Y.H. Park, J.S. Park & W.T. Jung Bridge scour countermeasures to minimize bridge failures during floods J. Lee, J. Park, M. Chung & K. Kwak

111 112

Bridge codes Distribution of demand in single-column-bent viaducts with irregular configuration in longitudinal direction R. Akbari & S. Maalek

117

Effective length factor of X-bracing system J. Moon, H.-E. Lee & K.-Y. Yoon

118

Monitoring system of suspension bridges and the utilization of recorded data C. Kawatoh, S. Kusuhara, S. Fukunaga & K. Endo

119

Reliability analysis of composite girder under positive and negative flexure designed by LRFD method D.K. Shin, J.S. Roh & E.Y. Cho

120

Flexural design of prestressed high-strength concrete girders W. Choi, H.C. Mertol, S. Rizkalla, P. Zia & A. Mirmiran

121

Strength prediction on the stiffened plates in compression Y.B. Kwon, D.W. Kang, B.H. Choi & T.Y. Yoon

122

Strength of fillet welded splices of SM570-TMC, extra thick plates J.B. Jo & J.W. Kim

123

Safety of ductility demand based seismic design for bridge columns J.-H. Lee, J.-H. Choi, J.-K. Hwang & H.-S. Son

124

An experimental investigation of the ultimate flexural behavior of steel tub girders with top lateral bracing B.H. Choi, T.Y. Yoon & Y.S. Park

125

Reliability based calibration of limit state bridge design code with material and member resistance factors I.Y. Paik & D.J. Bang

126

Bridge E-8 in the new railroad of high velocity to the northwest of Spain C. Jurado

127

A simple iterative method for determining the effective length of structural members in steel cable-stayed bridges D.-H. Choi, H. Yoo, D.-S. Lee & Y.-S. Kim

129

The influence of friction/sliding behavior of rubber bearing to the seismic performance of highway bridges K.Y. Liu, K.C. Chang, W.I. Chen & J.S. Hwang

130

Ultimate flexural strength of hybrid composite girders at sagging bending S.G. Youn, Y.T. Kim & D.B. Bae VII

131

Bridge inspection and diagnostics Application of data fusion technology on scour and siltation monitoring in river bed Z.J. Chen, W. Wang, S. Chen & S.H. Cao

135

Special tests of two post-tensioned concrete viaducts J. Ciesla, M. Lagoda & P. Olaszek

136

Active lamb wave propagation-based damage detection and location for steel plate W. Jeong, J. Seo & H. Kim

137

Settlement prediction model for pile foundation based on field observation X. Li, Z. Chen & X. Dong

138

Ambient vibration of stay cables used for damage detection in cable-stayed bridge C.-C. Chen, W.-H. Wu & J. Lin

139

Specials inspections and maintenances of prestressed concrete in Rio-Niterói Bridge C.H. Siqueira

140

Non-destructive testing of suspender ropes with magnetostriction M.S. Higgins & O. Tozser

141

Judging suitability of arch bridges for higher axle loading by load testing R.K. Gupta

142

Health assessment of pre-stressed concrete girder bridges by non-destructive testing R.K. Gupta

143

Optimal inspection and maintenance strategies for bridge network using supply and demand approach A.D. Orcesi & C.F. Cremona

144

Experimental investigations on the strength behavior of box beam and circular column connections Y.P. Kim & W.S. Hwang

146

Nondestructive evaluation of effective prestress using the core-drilling method S. Pessiki & M.J. McGinnis

147

Bridge safety management system by using Bridge Inspection Robot D.-j. Park, H.-g. Jung, B.-j. Lee, W.-t. Lee & J.-o. Kim

148

Matrix based cable-stay bridge cable force and deck elevation adjustments and FEM updating A. Turer

149

A regularization scheme for displacement reconstruction using measured structural acceleration data Y.H. Hong, H.W. Park & H.S. Lee

150

Dynamic testing of existing bridges for high speed trains A. Turer

152

Concrete bridge deck condition assessment with automated multisensor techniques D. Huston, J. Cui, D. Burns & F. Jalinoos

153

Parameter estimation of concrete bridge using ambient acceleration measured by wireless measurement system S.J. Lee, S.B. Kim, K.Y. Choi, G.Y. Song, D.O. Kang & Y.H. Lee VIII

154

Impact-Echo scanning for grout void detection in post-tensioned bridge ducts – Findings from a research project and a case history Y. Tinkey & L. Olson

155

Bridge management systems Design and implementation of a new bridge management system for the Ministry of Transport of Québec R.M. Ellis, P.D. Thompson, R. Gagnon & G. Richard

159

Comprehensive lightning protection technologies for mechanical and electrical systems of Sutong bridge B. Yao, W. Zhang, G. Chen & C. Jiang

161

Risk evaluation and management for road maintenance on urban expressway based on HELM (Hanshin Expressway Logic Model) Y. Sakai, K. Kobayashi & H. Uetsuka

162

Asset management system development J. Radic, J. Bleiziffer & G. Puz

163

Development of a smart-client based bridge management and maintenance system for existing highway bridges D. Shan & Q. Li

164

A new Bridge Management System for the National Department of Transportation of Argentina M.E. Ruiz, E.A. Castelli & T.A. Prato

165

Development of a bridge maintenance decision support module for Taiwan Bridge Management System H.-K Liao, C.-I. Yen & N.-J. Yau

166

Optimization of bridge management policies on the French national roads network N. Odent, J. Berthellemy, C.F. Cremona, A.D. Orcesi & M. Toriel

167

Bridge management: A challenge for local authorities B.M. Kamya

169

A condition index based on the concept of apparent age D. Zonta, F. Bortot & R. Zandonini

170

Design of the standardized measuring system for the integrated safety management of bridge structure W.S. Lee & K.T. Park

171

Bridges for high-speed railways Steel bridges for high speed railways – Design regarding fatigue and durability W. Hoorpah Dynamic response of the Cahir Viaduct – An investigation into the derailment of a freight train M. Majka & M. Hartnett A comfort limit for evaluating the serviceability due to bridge vibration B.G. Jeon, N.S. Kim & S.I. Kim IX

175

176 177

Vibration control through TMDs in high-speed railway bridges J.F. Henriques & J.M. Proença

178

DETAILS: A research project for improvement of analysis, design and durability of HS railway bridges G. Chellini, L. Nardini & W. Salvatore

179

Dynamic testing and numerical modelling of a typical short span high-speed railway bridge V. Zabel & M. Brehm

180

Development of an efficient finite element model for the dynamic analysis of the train-bridge interaction S. Neves, A. Azevedo & R. Calçada

181

Fatigue assessment of composite bridges for high speed railway traffic H. Figueiredo, R. Calçada & R. Delgado

182

Experimental modal analysis of a twin composite filler beam railway bridge for high-speed trains with continuous ballast T. Rauert, B. Hoffmeister, R. Cantieni, M. Brehm & V. Zabel

183

A study of the lateral dynamic behaviour of high speed railway viaducts and its effect on vehicle ride comfort and stability R. Dias, J.M. Goicolea, F. Gabaldón, M. Cuadrado, J. Nasarre & P. Gonzalez

184

Damage assessment Evaluating composite steel girder-concrete slab bridge beams using simplified plastic analysis P.S. McCarten Improving bridge component deterioration forecasting precision H.S. Kleywegt Stochastic subspace-based structural identification and damage detection – Application to a long span cable-stayed bridge W. Zhou & H. Li Structural safety of historical stone arch bridges in Korea N.K. Hong, H.-M. Koh, S.G. Hong & B.S. Bae

187 188

189 190

Realistic estimation method of moment redistribution in reinforced concrete beams based on the analytical methods J.H. Cheon, J.G. Park, S.C. Lee, M.S. Oh & H.-M. Shin

191

Probabilistic analysis of the structural behaviour of a bridge prestressed concrete beam C. Cremona, S. Mohammadkhani-Shali, B. Richard, C. Marcotte & B.Tonnoir

192

Gi-Lu Cable Stayed Bridge – From earthquake damage to full recovery Z.K. Lee, K.C. Chang, C.C. Chen & C.C. Chou

194

Stress monitoring of steel girder bridges with different boundary conditions N. Namatame, K. Tani, T. Tsuji, M. Kawatani, M. Kano, N. Tanaka & H. Hattori

195

Evaluation of compressive stiffness of elastomeric bearings H.J. Yoon, Y.J. Kim, C.B. Cho & I.J. Kwahk

197

X

Effect of soil-bridge interaction and continuity on live load distribution in integral bridges M. Dicleli & S. Erhan

199

Application of the analytic hierarchy process in performance evaluation of existing concrete cable-stayed bridge Q. Li, D. Shan & W. Yan

200

Analysis of box girder bridges using finite elements and AASHTO-LRFD R.R. Doerrer & R.A. Hindi Nonlinear finite element analysis of precast segmental prestressed concrete bridge piers H.-M. Lee, D.-J. Seong, J.-G. Park, K.-S. Kim, H.-M. Shin, T.-h. Kim, Y.-J. Kim & S.-W. Kim

201

203

Advanced numerical study of asphaltic surfacings on orthotropic steel deck bridges X. Liu, T.O. Medani & A. Scarpas

204

Estimation of damping characteristics for cable using system identification scheme S.-K. Park, K.W. Lyu & H.S. Lee

205

Self-adapting models of bridge degradation J. Bien & A. Banakiewicz

206

Computational model generation based on 3D CAD digital data of RC bridges J. Lee & M.-S. Kim

208

Artificial Intelligence: Historical development and applications in civil engineering field L. Sgambi

210

Safety factor prediction for steel cable-stayed bridges by iterative eigenvalue analysis D.-H. Choi, H. Yoo, D.-S. Kim & H.-S. Na

211

Damage assessment of existing bridges Evaluation of load-carrying capacity of the damaged bridge model using the updated FE model D.S. Jung & C.Y. Kim

215

Detection of sudden damages of structure by regularized autoregressive model using measured acceleration J. Kang & H.S. Lee

216

Internal damage localization in a thick plate using moving sensing windows Y.H. Kim, H.W. Park, J.W. Whang & H.S. Lee Hybrid health monitoring technique for PSC girders using wireless sensing and embedded monitoring algorithm J.H. Park, J.T. Kim, Y.S. Ryu, D. Mascarenas & M.D. Todd Regularization of inverse problem for damage detection I. Yoshida, C.W. Kim & M. Kawatani Feasibility investigation of health monitoring from traffic-induced vibration data of bridge M. Kawatani, C.-W. Kim & T. Fujimoto XI

217

218 219

221

Localization of damage in a bridge using measured response signals S. Shin & H. Park

223

Design and analysis Stonecutters bridge – Design for operation M. Carter & N. Hussain

227

Strut-and-Tie Method for FRP strengthened deep RC members S. Park & R.S. Aboutaha

228

Design of the Machang Mainbridge E.-H. Bae, S.-Y. Kim, R.-G. Kim, S. Hopf, A. Patsch & P. Walser

229

Durability of suspension bridge with multi main spans M. Inoue, M. Kudo, K. Doi & Y. Takizawa

230

Effect of main steel corrosion on the stiffness of corroded reinforced concrete beams F.J. O’Flaherty, P.S. Mangat, P. Lambert & E.H. Browne

232

Optimum life-cycle-cost design for bridge structures considering damage probability Y.S. Shin, J.H. Park & T.H. Kim

233

The study on the methods for slimming bridge K.H. Kim, C.S. Lee, K.S. Hong & C.-G. Lee

234

Design of deck continuity details for steel and prestressed concrete bridges A.P. Ranasinghe & W.L. Haugeto

235

Reliability-based optimum design of high-speed railway bridges considering structure-rail interaction J.-S. Lee, H.-N. Cho & Y.-R. Ihm

236

Cyclic response of the precast SRC bridge piers Y.-S. Chung, C.S. Shim, J.-Y. Yoon & J.-H. Park

237

General design method for the shear connection according to failure modes C.S. Shim, S.-M. Jeon & P.-G. Lee

238

Structural system durability through jointless bridge decks U.B. Attanayake, A.E. Ulku & H.M. Aktan

239

Modal flexibility-based FEM model updating for bridges J. Cui, D. Kim, K.Y. Koo & H.Y. Jung

241

Optimal design of a steel box girder bridge considering aesthetics Y.S. Shin, J.H. Park & G.O. Kim

243

Complex shapes and innovative technologies for bridges I. Paoletti

244

Reliability-based design optimization using a response surface method S.C. Kang & H.-M. Koh

245

Durability design procedure of concrete structures in Korea using partial safety factor format J.S. Kim, K.J. Shin, J.H. Kim, K.M. Lee & S.H. Bae Analysis of static behavior of CFTA girder H. Lee, K.-H. Park & J.-S. Kong

246 247

XII

Durability analysis of RC bridges using Monte-Carlo simulation W. Raphael, R. Faddoul & J. Hokayem System stability design of cable-stayed bridges based on elastic/inelastic system buckling analyses Y.-S. Kyung, J.-S. Lee & M.-Y. Kim

248

249

Experimental research on passive cable dampers’ performance S.-s. Ahn, J.-H. Park & S. Lee

251

Conformity control of concrete based on the “concrete family” concept R. Caspeele & L. Taerwe

252

Effective slab width in steel-concrete composite girder bridges D. Bae, S.G. Youn & Y.S. Park

253

Preference-based optimal maintenance planning for deteriorating bridges S.Y. Lee, W. Park, H.-M. Koh & H.J. Kim

255

Analysis of steel-soil bridge structure made of corrugated plate D. Beben & Z. Manko

256

Introduction of design for concrete filled steel tubular arch girder with external tendons E. Lee, H. Park, M.G. Park, K.H. Park, S.Y. Lee & J.H. Kim

258

Design expectations, monitoring response and maintenance decisions Design expectations and monitoring response of the Certosa fly-over in Milan (Italy) P.G. Malerba, A. Giussani, G. Pezzetti & C. Malerba

263

Statistical monitoring of concrete structures and cable-stayed bridges A. Fassò & G. Pezzetti

264

Short and long term monitoring for maintenance and retrofitting of existing bridges C. Modena, P. Franchetti, M. Grendene & M. Frizzarin

266

The structural analysis of the Messina Strait Bridge F. Bontempi

267

Influence of large displacements on the structural stability of cable supported bridges F. Biondini, P. Limonta, P.G. Malerba & R. Stucchi

268

Wind-induced fatigue assessment in main cables and hangers of suspension bridges F. Ubertini & F. Bontempi

269

Development of the advanced robot systems for bridge inspection and monitoring Introduction of the Bridge Inspection Robot Development Interface (BIRDI) J.S. Lee, I. Hwang, H.S. Lee & S.H. Hong

273

Robotic diagnosis system for detection of bridge structures D.-J. Moon, K.-T. Yang, S.-S. Nam & K.-H. Im

274

Development of bridge inspection robot system: Wall climbing robot and flying robot I.M. Koo, C.M. Lee, S.-H. Whang, D.-H. Kim, M.-S. Kang, K. Cho, W.-H. Son, S. Park, S.K. Park & H.R. Choi

275

XIII

Bridge inspection robot system with novel image processing J.-K. Oh, A.-Y. Lee, S.M. Oh, Y. Choi, B.-J. Yi, H.W. Yang, J.H. Lee & Y.S. Moon

276

Intelligent bridge management system based on the image data from robotic devices S. Kim, J.S. Lee, Y. Choi & Y.S. Moon

277

Optimum NDT using infrared thermography for defected concrete G. Zi, J.G. Sim, H. Oh & J. Lee

278

A development of repair mechanism and control technologies for bottom part of concrete bridge K.-Y. Lim

279

Fatigue analysis Evaluation of fatigue strength of one riveted historical railway bridge A. Pipinato, C. Pellegrino & C. Modena Global-local finite element analysis of riveted railway bridge connections for fatigue evaluation B.M. Imam, T.D. Righiniotis & M.K. Chryssanthopoulos

283

284

Fatigue of riveted metal structures T. Larsson & O. Lagerqvist

285

Managing fatigue susceptible details on critical railway bridges at CN J.A. Cavaco

286

Influence of the fatigue resistance of duplex steel on the bridge design – A span length investigation T. Rauert, B. Hoffmeister, A. Gieseking & O. Hechler Fabrication procedure effects on fatigue resistance of steel orthotropic deck welds H.B. Sim, C.M. Uang & C. Sikorsky Estimation of low-cycle fatigue strength of steel structural members under earthquake loading J. Iyama & J.M. Ricles Variability analysis of fatigue crack growth rates of materials from ancient Portuguese steel bridges J.A.F.O. Correia, A.M.P. Jesus, M.A.V. Figueiredo, A.S. Ribeiro & A.A. Fernandes Assessment of the coupled effect of corrosion-fatigue on the reliability of RC bridges E. Bastidas-Arteaga, M. Sánchez-Silva, Ph. Bressolette, A. Chateauneuf & W. Raphael An optimal design of TMD for the improvement of fatigue reliability of steel-composite high-speed railway bridges using target performance approach S.-J. Kim, S.-C. Kang, H.-M. Koh & W. Park

287 288

289

290

292

293

Fatigue damage of orthotropic steel bridge decks and its retrofit T. Shimozato, T. Yabuki, Y. Arizumi, Y. Hirabayashi, N. Inaba & S. Ono

294

Fatigue design for highway bridge ancillary structures Y.C. Park, S. Roy & R. Sause

295

XIV

Fiber reinforced composites in bridges On mechanical performance of different type of FRP beams as reinforcement of pedestrian bridge G. Boscato & S. Russo

299

Shaping composite bridges for traffic and the environment R.A. Daniel

300

A study on the dynamic behavior of a CFRP cable J. Park & K.J. Hong

301

Composite ‘Delta Deck’: The promising bridge deck for new and rehabilitated bridges S.W. Lee & K.J. Hong

302

Advanced removable connection for glass fiber reinforced polymer bridges D.-U. Park, K.-J. Hwang & J. Knippers

303

Full pultruded FRP profile structures M.D.G. Pulido

304

Health monitoring Detachable sensor for bridge cable maintenance and safety S. Sumitro, H. Hoashi, T. Okamoto & M.L. Wang

307

Stock Condition Index analyses response to Bridge Condition Index determinations P.S. McCarten

308

Traffic-induced vibration of bridges: Input force identification C.-H. Loh, A.-L. Wu & J.-H. Weng

309

Turning the Humber Bridge into a smart structure N.A. Hoult, P.R.A. Fidler, C.R. Middleton & P.G. Hill

310

Application of data fusion in the safety monitoring of Sutong Bridge foundation Z.J. Chen, L. Bian, T. Xue & X.W. Zhang

311

Remote measurement of crack length in sacrificial test piece by self-reference lock-in thermography Y. Sakino, T. Sakagami & Y.-C. Kim

312

Wind-induced vibrations and countermeasures for cable systems on long-span bridges I. Yamada, S. Kusuhara, K. Fumoto & N. Toyama

313

Structural monitoring of a bridge prestressed concrete beam under loading C. Cremona, C. Tessier, V. Le Cam, B. Tonnoir, R. Leconte & V. Barbier

314

Application of InSAR on ground deformation in the location of Sutong Bridge Z.J. Chen, N.N. Zhang, X.Y. Li & L.Y. Feng

316

Long-term structural health monitoring of the Torino’s pedestrian cabled-stayed bridge L.M. Giacosa & A. De Stefano

317

Identifying bridge damage using Brillouin Optical Fiber Sensing W. Zhang, B. Shi, Y.Q. Zhu & Y.F. Zhang

318

Innovative treatment of monitoring data for reliability-based structural assessment T.B. Messervey & D.M. Frangopol

319

XV

Life-cycle monitoring of the structural configuration of a suspension bridge H.-K. Kim, H. Lee, J.-H. Jang, Y.-H. Kim & S.-K. Ro

320

Bridge monitoring while partial demolition under traffic K. Zilch, E. Penka, M. Hennecke, U. Willberg, Th. Wunderlich & Th. Schäfer

321

Development and implementation of a low-cost, continuous bridge health monitoring system Y.-S. Lee, B.M. Phares & T.J. Wipf

322

Structural health monitoring of civil infrastructures using MEMS-based technologies T. Miyashita & M. Nagai

324

Error-resilient routing for wireless SHM powered by solar cells J. Ryu, J. Kim, I. Yeo, Y. Cho & H. Shin

326

Correlation analysis on long term monitoring data of Donghai Bridge L. Sun, Z. Min & D. Dan

327

Low-latency routing for wireless SHM powered by solar cells J. Kim, Y. Cho, J. Ryu, I. Yeo & H. Shin

328

Health monitoring for corrosion detection in reinforced concrete bridges A. Del Grosso, F. Lanata, L. Pardi & A. Mercalli

329

Investigation of the relationship between displacement and acceleration in nonlinear dynamics using chaos theory analysis R.A. Livingston & S. Jin

330

The application of the frequency-shifted feedback laser optical coordinates measurement system for field measurement of bridges in service S. Umemoto, N. Miyamoto, K. Kubota, T. Okamoto, T. Hara, H. Ito & Y. Fujino

331

Bridge-Weigh-In-Motion based on strain measurement of vertical stiffeners E. Yamaguchi, Y. Naitou, K. Matsuo, Y. Matsuki & S. Kawamura

332

An FIS and AHP based on line evaluation system on Donghai Bridge D. Dan, L. Sun, Z. Yang & D. Xie

333

Structural health monitoring of complex structural systems using adaptive models S. Arangio

336

Information technology for lifetime management of bridge A Strategy for IT-based lifetime management of bridge S.-H. Lee, B.-G. Kim, H.-J. Kim & S.-J. Kim

339

Use of information technology in a regional bridge management contract R. Kiviluoma & M. Tervo

340

Development of a structural health monitoring system with wireless sensor networks H. Emoto, A. Miyamoto & K. Kawamura

342

Development of a multi-purpose remote health monitoring system for existing bridges A. Miyamoto, J. Sonoda & K. Kawamura

344

Automated identification of modal properties in a steel bridge instrumented with a dense wireless sensor network A.T. Zimmerman, R.A. Swartz & J.P. Lynch XVI

345

Downsizing seismic sensing system and its implementation Y. Mizuno & Y. Fujino

346

SHM sensor networking with remote powering and interrogation M.D. Todd, D. Mascarenas, E. Flynn, B. Lee, K. Lin, D. Musiani, T. Rosing, R. Gupta, S. Kpotufe, D. Hsu, S. Dasgupta, G. Park, K. Farinholt, M. Nothnagel & C. Farrar

348

Development of an advanced inspection system for weathering steel bridges based on digital image recognition S. Goto, T. Aso & A. Miyamoto

349

A study on the self-anchored suspension bridge behavior using GPS H.J. Ham, S.H. Oh, I.H. Bae & G.H. Ha

350

SHM role in Bridge Life Cycle Analysis (BLCA) S. Alampalli & M. Ettouney

351

Interoperable information model based on IFC for the cable-stayed bridge monitoring system J.-H. Yi, H.J. An, H.-J. Kim & S.-H. Lee

352

An automatic crack recognition system for concrete bridge inspection by image processing approach A. Miyamoto

353

Innovative construction technology Erection of asymmetric pylon table and geometry control of Machang cable-stayed bridge H. Lim, M. Kim & J. Seo

357

Experimental study on the stability of temporary support for girder construction K. Ohdo, S. Takanashi & H. Takahashi

358

Design of Cheong-Poong (steel-concrete hybrid cable-stayed) bridge D.-H. Yoo, J.-S. Ko & J.-G. Paik

359

Influence of initial imperfections on stability of temporary support for bridge girder H. Takahashi, K. Ohdo & S. Takanashi

360

Analysis for initial equilibrium condition and erection stages of Sorok (Self-Anchored Suspension) Bridge Y. Son, D. Yoo, S. Jeong & T. Yoon

361

Seosang bridge movable scaffolding system A.A. Póvoas

362

The construction of Machang cable-stayed bridge M. Kim, J. Seo, J. Song & H. Lim

363

Construction planning and analysis of six continuous extradosed PSC bridge S. Kim, J.W. Seo, Y. Lee & I. Seo

364

Underpass in the street O’Donnell in Madrid C. Jurado

365

Construction of P.S.C. Box girder bridge (F.C.M) which pre-compensation method is applied to H. Jee, J.H. Shim, M.K. Min & H.J. Lee XVII

367

Large scale cyclic tests of precast segmental concrete bridge columns with unbonded post-tensioning tendons Y.-C. Ou, G.C. Lee, P.-H. Wang, M.-S. Tsai & K.-C. Chang

368

Key-segment closing method using artificial heat for partially earth-anchored cable stayed bridges with classical span length J.H. Won, K.I. Cho, J.H. Yoon & S.H. Kim

369

Highway bridges made of circular hollow sections U. Kuhlmann & M. Euler Monitoring of early stage prestress change of long span stream-cured concrete box girder with pretension method K.-Y. Choi, G.-Y. Song, D.-O. Kang & S.-W. Cha Effect of deformation of spans on serviceability of composite highway bridge Z. Manko

370

371 373

Integrated assessment – Practical application of probabilistic methods Guideline for probabilistic assessment of deteriorated bridges J. Lauridsen, F.M. Jensen & S. Engelund

377

Optimization of special inspections of concrete bridges S. Engelund & M. Sloth

378

Probability based assessment of railway bridges in Denmark – Previous applications, current state and future possibilities J.S. Jensen, D.F. Wisniewski & O.B. Ulstrup

379

Probability based assessment of motorway bridges in Denmark J. Bjerrum, A. O’Connor, C. Pedersen & I. Enevoldsen

380

Probability based assessment of a large riveted truss railway bridge A. O’Connor, C. Pedersen, I. Enevoldsen, L. Gustavsson & J. Hammarbäck

382

Integrating health monitoring and lifecycle management of bridge and highways Integrating human, natural and engineered systems and associated paradigms for infrastructure asset management F. Moon, P. Gurian, F. Montalto & A.E. Aktan

387

Structure and infrastructure health monitoring as a key enabling paradigm for integrated asset management F. L. Moon, A.E. Aktan, F. Jalinoos & H. Ghasemi

389

Integration of health monitoring in asset management in a life-cycle perspective T.B. Messervey & D.M. Frangopol

391

Challenges for asset management in W-Europe L.(H.E.) Klatter

392

Effective bridge management using ABMS H. Kawamura, K. Kudo, M. Soma, H. Kawaragi & M. Kaneuji

393

Development of BMS and possibility of performance based contracting using BMS M. Kaneuji, H. Kawamura, M. Soma & E. Watanabe

394

XVIII

A study on LCC prediction for bridge management taking future uncertainty into account K. Mitsunari, Y. Takahashi & Y. Otani

396

Load testing and analysis of bridges missing critical documentation J. Prader, J. Weidner, H. Hassanain, F. Moon, E. Aktan, F. Jalinoos, B.Buchanan & H. Ghasemi

397

Integrating health monitoring in asset management H. Furuta, H. Hattori, T. Ohama, K. Yoshida & D.M. Frangopol

398

Integrative research supporting decision making for bridges F.N. Catbas, D.M. Frangopol & A.E. Aktan

399

Development of affordable GPS displacement monitoring system M. Saeki, K. Oguni & M. Hori

400

Methods for measuring structural deflection and applications to bridge deck performance monitoring J.M.W. Brownjohn & X. Meng Experimental identification of multiple oscillation frequencies using GPS P.A. Psimoulis, S. Pytharouli & S. Stiros Real-time dynamic monitoring with GPS and georobot during Sutong Bridge construction S.X. Huang & B.C. Yang

401 402

403

The safety assessment method of existing large span steel structural members X. Liu & Y. Luo

404

A mechanical model of steel frames with joint damages Y. Luo & H. Song

405

Statistic analysis of a prototype structural health monitoring system for the Nanpu Bridge in Shanghai, P. R. China R. Wang, X. Meng, Y. Luo, L. Yao & W. Huang

406

The analysis of GPS single epoch positioning algorithm based on the deformation monitoring L. Yao, P. Yao & X. Meng

407

Deformation analysis of the supporting towers of the Nanpu Bridge from GPS measurements L. Yao, Y. Xie, Y. She & X. Meng

408

Deformation monitoring and analysis of high pylon of Su-Tong Bridge in construction D. Yue, C. Wang & H. Li

409

The statistical investigation on one year GPS monitoring data from Donghai Bridge Health Monitoring System (DHBHMS) D. Dan, L. Sun, X. Meng & D. Xie

410

Nonlinear dynamic responses of large span hybrid structures under multi-dimensional seismic excitation Y. Huang & Y. Luo

411

XIX

Research into the use of GNSS to monitor the deflections of suspension bridges, and the role of the FIG in deformation monitoring of bridges G.W. Roberts, X. Meng & C.J. Brown

412

Deflection monitoring of bridges: A case study of the Forth Road Bridge X. Meng, G.W. Roberts & C.J. Brown

413

Recent progress in GNSS-based long bridge deformation monitoring X. Meng, G.W. Roberts, A.H. Dodson, L. Xu & Z.Wan

414

Investigation on the severe corroded steel girder bridge, Hakkeibashi-Bridge H. Furuta, M. Kawatani, T. Yamaguchi, I.H. Kim & M. Soma

415

System of partial safety factors in reliability-based bridge assessment I. Paik, D. Kim & S. Shin

417

Bridge management system for national highway network in Korea H.Y. Kim

418

Autonomous bridge inspection and monitoring based on the robotic systems J.S. Lee, S. Kim, I. Hwang & J.F. Choo

419

Development of inspection robot to PSC box bridge using digital image processing J. Kim, B. Lee, D. Park, J. Shin & C. Park

420

Quantification models of bridge condition and performance K.-J. Lee, S.-H. Park, J.-S. Kong, K.-H. Park & C.-H. Park

421

Structural behaviors of Seohae cable-stayed bridge affected by temperature S.G. Kang, J.B. Kwon, I.K. Lee & G.H. Lee

422

Influences of diffusion coefficient and verification of validity on prediction of chloride induced deterioration of concrete bridges H. Tsuruta, H. Furuta, I. Iwaki, A. Kamiharako, M. Soma & M. Suzuki

423

Life cycle costing Life time assessment of steel bridges via monitoring and testing U. Peil, M. Frenz & I. Schendel

427

Life cycle cost evaluation of neutralized reinforced concrete bridges subjected to earthquake Y.C. Sung, C.K. Su, C.C. Hsu, M.C. Lai, K.Y. Liu & K.C. Chang

428

Degradation, repair methods and real service life of soil steel composite bridges in Sweden H.-Å. Mattsson & H. Sundquist

429

Study on function extension of an existing PC rigid frame bridge during its life cycle X.-X. Li, X.-F. Shi, X. Ruan & T.-Y. Ying

430

Residual life assessment of steel girder bridges R.K. Gupta

431

Application of a new metal spraying system for steel bridges Part4. Reference product service life prediction for the system T. Kondo, S. Okuno, A. Yamazaki & H. Matsuno Resource allocation for seismic retrofit of highway network U.J. Na, M. Shinozuka, P. Franchetti, E. Da Lozzo & C. Modena XX

432 433

Probabilistic cost model for bridge integrated project delivery and management M.G. Huang, B.G. Kim, S.H. Lee & Y.H. Park

434

Reliability analysis for bridge piles A.S. Nowak, M. Kozikowski, T. Lutomirski & J. Larsen

435

Influence of chloride ion diffusion coefficient on the service life of concrete structures subjected to coastal environment J.I. Park, S.H. Bae, K.G. Yu, K.M. Lee, H.Y. Shin & D.O. Kang

436

Damage to structures due to increasing traffic numbers related to service life predictions A. de Boer & B.(M.H.) Djorai

437

Optimal design of cable-stayed bridges based on minimum life-cycle cost S.-H. Han & A. H-S. Ang

439

Design planning decision for deteriorating wearing surfaces based on whole-life design considering life-cycle cost J.X. Peng, X.D. Shao & M.G. Stewart Optimal seismic design of cable-stayed bridges based on LCC concept D. Hahm, H.-M. Koh, W. Park, K.-S. Park & S.-Y. Ok

440 442

Life-cycle structural engineering Structural geometry effects on the life-cycle performance of concrete bridge structures in aggressive environments F. Biondini, D.M. Frangopol & P.G. Malerba

445

FRP reinforced concrete: Reliability assessment for life-cycle analysis S.M.C. Diniz

446

Seismic performance upgrading of existing bridge structures G. Furlanetto, L. Ferretti Torricelli & A. Marchiondelli

447

Estimation of fatigue life for suspension bridge hangers under wind action and train transit F. Petrini, F. Giuliano & F. Bontempi

448

Life-cycle bridge management considering member interference K.-H. Park, S.-Y. Lee & J.-S. Kong

449

Bridge maintenance strategy based on life-cycle cost and rebuild cost stabilization A. Miyamoto & J. Ishida

450

Damage modeling and life-cycle reliability analysis of aging bridges F. Biondini, D.M. Frangopol & E. Garavaglia

452

Lifetime-perspective design of Kwangyang suspension bridge with main span 1545m The planning and design of the long-span suspension bridge connecting Myodo and Gwangyang in Korea J.-H. Kim, M.-J. Lee, S.-H. Shin & S.-B. Chun Wind resistance design of Kwangyang Bridge S.-D. Kwon, S.-H. Lee, H. Uejima & M.-J. Lee

455 456

XXI

Planning, design and construction of the largest concrete pylon in the world S.-H. Lee, W.-S. Jang, S.-B. Oh & K.-T. Kim

457

The design for anchorage of sea-crossing long-span suspension bridge H.-S. Jang, Y.-I. Jang, Y.-S. Choi, K. Park & K.-T. Kim

459

IDC for economical and safe design for the suspension bridge connecting Myodo and Gwangyang C.-S. Kim, W.-J. Kim, K.-S. Cho, J.-H. Kim & Y. Yamasaki

460

The innovative construction method for the long-span suspension bridge connecting Myodo and Gwangyang in Korea S.-H. Shin, P.-J. Yu, S.-W. Jeong & Y. Takizawa

461

The planning of ship collision protections based on risk analysis H.-C. Kwon, M.-J. Lee, J.-H. Park & H. Andersen

462

Measurement and evaluation of data from wind observation station in Gwangyang S.-L. Lee, G.-M. Han, Y.-S. Gwon & Y.-G. Bae

463

Vehicle-structure dynamic interaction by displacement constraint equations and stabilized penalty method K.-Y. Chung, J.-M. Kim, M.-K. Song & J.-G. Paik

464

Loads and capacity assessment Evaluation of ultimate capacity of deteriorated reinforced concrete bridge columns M. Tapan & R.S. Aboutaha

467

Load test of bonded post-tensioned concrete beams with corroded tendon S.G. Youn, S.H. Park, C. Lee & E.K. Kim

468

The bridges and the floods V. Popa

470

3 DOFs collision model for the analysis of bridge super-structures and deck house collision G.H. Lee & S.L. Lee

471

Modelling granular soil to predict pressures on integral bridge abutments J. Banks, T. Knight, J. Young & A. Bloodworth

472

Assessment of bridge capacity through proof load testing J.D. Gómez & J.R. Casas

473

Micro-simulation modelling of traffic loading on medium- and long-span road bridges E.J. OBrien, A. Hayrapetova & C. Walsh

474

Nonlinear analysis of PSC structures with internal tendon by strengthened using external tendon J.G. Park, J.-H. Cheon, M.-Y. Kim, H.M. Shin, B.-J. Lee & J.-H. Choi Enhancement of bridge serviceability due to a strong wind A. Krecak, P. Sesar & M. Masala-Buhin Comparison of theoretical and measured temperature distributions for concrete slab bridges E.-S. Hwang & J.J. Lee XXII

475 476

477

Numerical analysis of old masonry bridges supported by field tests J. Bie´n, T. Kami´nski & Ch. Trela Input ground motion for seismic design considering near fault effects in stable continental regions J.H. Kim & J.K. Kim

478

479

Calculation of dynamic interaction of train and an arch bridge J. Györgyi & G. Szabó

480

Structural behavior of corroded reinforced concrete structures K.Z. Hanjari, K. Lundgren, P. Kettil & M. Plos

481

Field evaluation of dead and live load hanger rod stresses in a continuous steel girder bridge S. Pessiki & I. Hodgson

482

Dynamic behaviour of soil-steel road bridge made from corrugated plates D. Beben & Z. Manko

483

Development of live load model using Weigh-In-Motion data E.-S. Hwang, I.R. Paik & J.-J. Lee

485

Bridge safety analysis considering heavy truck loading J. Du & D.-J. Han

487

Behaviors of bracing members in U-type trapezoidal steel box girders K. Kim & J.H. Park

488

Monitoring and assessment of bridges using novel techniques Wireless sensor networks for model based bridge monitoring S. Deix, M. Ralbovsky & R. Stütz Structural health monitoring and passive vibration control of an Austrian road bridge M. Reiterer & L. Praxmarer

491

492

Recent Austrian activities in bridge monitoring R. Geier

493

Computational model updating for bridge maintenance planning S. Deix, M. Ralbovsky & H. Friedl

494

AIFIT – user orientated identification for infrastructure, theory R. Wendner, S. Hoffmann, A. Strauss & K. Bergmeister

495

AIFIT – user orientated identification for infrastructure, application S. Hoffmann, R. Wendner, K. Bergmeister, M. Mautner & W. Steinhauser

496

Stochastic nonlinear finite element analysis of bridges R. Pukl, M. Voˇrechovský & D. Novák

498

Overview of 40 bridge monitoring projects using fiber optic sensors D. Inaudi & B. Gliši´c

499

Reliability assessment of an existing bridge using long-term monitoring A. Strauss, D.M. Frangopol & S. Kim

500

XXIII

Evaluation of the redundancy of bridge superstructures and substructures M. Ghosn & D.M. Frangopol

501

Damage detection by pattern recognition at bridge components H. Wenzel & R. Veit-Egerer

502

Dynamic damage identification of Colle Isarco viaduct D. Lehký, D. Novák, P. Frantík, A. Strauss & K. Bergmeister

504

Virtual testing of bridges for life cycle reliability assessment ˇ R. Pukl, V. Cervenka, B. Teplý, D. Novák & K. Bergmeister

505

Degradation modelling of bridge components based on cellular automata D. Novák, B. Teplý, J. Podroužek, M. Chromá & A. Strauss

507

Stochastic aging model for infrastructure buildings M. Petschacher

508

New developments in large-scale model studies of bridge components and systems subjected to earthquakes Hybrid distributed simulation of a bridge-foundation-soil interacting system A.S. Elnashai, B.F. Spencer, S.J. Kim, C.J. Holub & O.S. Kwon

511

Research and application of precast segmental bridge columns for seismic regions K.-C. Chang, M.-S. Tsai, Y.-C. Ou, G.C. Lee, J.-C. Wang & P.-H. Wang

512

Seismic performance of a two-span bridge subjected to fault-rupture H. Choi, M.S. Saiidi, P. Somerville & S. El-Azazy

513

Nonlinear modeling of a two-span reinforced concrete bridge model from pre-yield through failure utilizing contemporary analytical methods N. Johnson, M. Saiidi & D. Sanders

514

Development of an innovative seismic damper for large-scale bridges and sub-structured hybrid earthquake loading tests H. Iemura, A. Igarashi & A. Toyooka

515

Practical application of BMS and BMS-DB Decision making processes and deterioration models of bridge management systems in Korea B.-G. Kim, J.-N. Park, S.-H. Lee & M.-S. Park

519

J-BMS database system 2007 for management of existing bridges in Yamaguchi prefecture K. Kawamura, A. Miyamoto & J. Ishida

520

Practical application of J-BMS to existing bridges in Yamaguchi Prefecture A. Miyamoto, K. Kawamura & J. Ishida

521

Rational approach for the management of a medium size bridge stock E. Brühwiler

522

Proposal for BMS deterioration curves based on the analysis of Hanshin Expressway inspection data H. Nakajima, T. Yamagami, T. Kagayama & M. Hayashida XXIV

523

Methodology for determination of financial needs of gradually deteriorating bridges B.T. Adey & R. Hajdin The measure towards advanced of Bridge Management System for Expressway Bridges in Japan Y. Wada, S. Sakai, T. Ohshiro, A. Homma & N. Ogata Application of China bridge management system in Qinyuan city B.F. Yan & X.D. Shao

524

525 526

Practical applications of SHM techniques for railway systems Structural monitoring of a maglev guideway with wavelength division multiplexed FBG sensors W. Chung, D. Kang, I. Yeo & J.S. Lee

529

Evaluation of modal parameters of a full scaled prestressed concrete beams for railway bridges S.I. Kim & N.S. Kim

530

Practical acceleration reducing method in high-speed railway bridges W.J. Chin, J.W. Kwark, J.R. Cho, E.S. Choi & B.S. Kim

531

Real-time damage detection of railroad bridges using acceleration-based ANN algorithms J.T. Kim, J.H. Park, D.S. Hong & J.H. Yi

532

Active piezoelectric sensor nodes and sensor self-diagnosis for structural health monitoring S. Park, C.B. Yun, G. Park & D.J. Inman

533

Modal parameter extraction of high-speed railway bridge using TDD technique B.H. Kim, J.-W. Lee & T.-Y. Yoon

534

Reliability and risk management Challenges for structural maintenance in coastal and offshore zones – Floating structures E. Watanabe

537

Reliability analysis of Steel – Concrete Hybrid Cable-Stayed Bridge during construction J.H. Yun, C. Moon, J.W. Sun & H.N. Cho

539

Reliability analysis of a high-speed railway bridge system based on an improved response surface method A.S. Nowak, T. Cho, D.H. Lee & M.-K. Song

540

ANN-based reliability analysis of a fiber reinforced polymer deck J. Cui, D. Kim & D.H. Kim

542

Strength of the chain for suspended scaffolds Y. Hino

543

Multimode analysis of extraneously induced excitation due to turbulence on cable-stayed bridges, including temporary stabilizing measures J.-Y. Cho, Y.-R. Cho & H.-E. Lee XXV

544

Reliability assessment of seismic expansion joints in bridges J.E. Padgett & R. DesRoches System-level reliability evaluation of bridge structures and networks by matrix-based system reliability method J. Song & W.-H. Kang

545

546

Rehabilitation and monitoring of a marine bridge in Ireland A. Farrell, L. Duffy, A. O’Connor & J. Kelly

547

Repair of damaged footbridge after strike of excavator A.G. Mordak & Z. Manko

549

Effect of corrosion on the reliability of a bridge based on Response Surface Method S.I. Jo, T. Onoufriou & A.D. Crocombe

550

Vibration control of cable-stayed bridge and derrick crane system during construction H.-J. Pae, D.-S. Kim, W. Park, K.-S. Park & H.-M. Koh

551

Repair and strengthening Ductility of CFRP strengthened concrete bridge girders S. Kim & R.S. Aboutaha Modal analysis and step-by-step repair operation of a two span concrete skew bridge to replacement of its elastomeric bearings R. Akbari, S. Maalek & H. Ashayeri Bridge widening – technical, economical and aesthetical aspects G. Boro´nczyk-Plaska & W. Radomski

555

556 557

Behavior under compressive loads of steel structural members repaired by heating and pressing M. Hirohata & Y.-C. Kim

558

Effectiveness of prestressed Carbon Fibre Reinforced Polymer (CFRP) sheets for rehabilitation of prestressed concrete girders Y.J. Kim, M.F. Green, C. Shi, J. Ford, L. Bizindavyi & R.G. Wight

559

The use of polymer concrete materials for construction, maintenance, rehabilitation and preservation of concrete and steel orthotropic bridge decks A.M. Dinitz & S. Park

560

The correlation between crack and residual stress generated by repair welding in service Y.C. Kim, S.H. Lee & Y. Agano

561

Repair of a concrete bridge by composites CRFP M. Abdessemed, S. Kenai, A. Kibboua, J.-L. Chatelain, B. Guillier & A. Bali

562

Innovative rehabilitation of a damaged prestressed concrete girder bridge using prestressed CFRP sheets: Design and specification Y.J. Kim, M.F. Green, G.J. Fallis, R. Eden & R.G. Wight

563

Rehabilitation of bridges with concrete overlays C.A.M. de Smet & J. Kunz

564

Bond and flexural behaviour of RC members strengthened with CFRP composites D.S. Yang, J.M. Park, S.N. Hong & S.K. Park

566

XXVI

Seismic performance improvement of bridges by earthquake protection systems in Korea D.-H. Ha, H.-M. Koh, S.Y. Lee, H.J. Kim & I.J. Kwahk

567

Application of new prestressing method using carbon fiber plates T. Ohshiro, Y. Wada, A. Takeuchi, K. Morikita, H. Yasumori & T. Takahashi

568

Experimental study of bolted joint with ultra thick plate and M30 bolt J. Kim, J. Byuoun, J.B. Jo & K. Jung

569

Monitoring for fatigue crack propagation of steel plate repaired by CFRP strips H. Nakamura, K. Maeda, H. Suzuki & T. Irube

570

Reevaluation of stresses and displacement of horizontally curved girders of a continuous span bridge D.J. Kim, C.P. Fan & B.T. Yen

573

Railroad bridge replacement in the US today: Current technology and future possibilities F. Moreu, T. Nagayama, J. Zeman, G. Rus, S.Y. Lee & T. Park

575

Assessment of repair cost and service life of repaired concrete structures after chloride attack H.-W. Song, A. Petcherdchoo & H.-B. Shim

577

Tests on cast iron carried out to repair bearings in Tumski Bridge in Wroclaw (Poland) Z. Manko

579

Research & applications for bridge health monitoring Residual structural performance of corroded steel tubes submerged in seawater K. Sugiura, E. Watanabe, K. Nagata & I. Tamura

583

Modal flexibility and curvature for damage assessment: Laboratory demonstrations M. Gul & F.N. Catbas

585

Benchmark studies for Structural Health Monitoring using computer vision R. Zaurin & F.N. Catbas

587

Field monitoring of continuous steel-concrete composite girder during internal force adjustment of the Siyuan Bridge W. Lu & D.M. Frangopol

588

Application of GPS monitoring technology to the construction of the pylon J.S. Lee & J.G. Yoon

589

Bridge fatigue reliability assessment and prediction K. Kwon & D.M. Frangopol

590

Eigenfrequency estimation for bridges using the response of a passing vehicle with excitation system Y. Oshima, Y. Kobayashi, T. Yamaguchi & K. Sugiura

591

Monitoring and inspection of a 30 years old prestressed concrete bridge M. Pimentel, J. Santos, J.R. Casas & J. Figueiras

592

Boundary condition parameter estimation for structural identification Y. Dere & F.N. Catbas

593

XXVII

Long-term monitoring of stochastic characteristics of a full-scale suspension bridge H.-B. Yun, S.F. Masri, R.D. Nayeri, F. Tasbihgoo, E. Kallinikidou, M. Wahbeh, R.W. Wolfe & L.-H. Sheng The need, challenges, and opportunities for research and application of Bridge Health Monitoring, a Turkish Experience A. Turer Crack detection in steel bridges F. Jalinoos & A. Rezai

594

595 596

Systems-based monitoring approaches for improved infrastructure management under uncertainty: Novel approach F.N. Catbas & D.M. Frangopol

597

Seismic and dynamic analysis Prioritization and seismic risk assessment of bridges D. Cardone, G. Perrone, M. Dolce & L. Pardi

601

Ambient vibration test and seismic evaluation of steel-deck truss bridge S. Jung, S.-T. Oh, S. Kim, Y.-W. Shim & S.S. Chen

603

Finite element model updating of a concrete arch bridge through static and dynamic measurements H. Schlune, M. Plos, K. Gylltoft, F. Jonsson & D. Johnson

605

Seismic response of highway viaducts under design live load considering vehicle as a dynamic system M. Kawatani, C.-W. Kim, S. Konaka & R. Kitaura

606

A substructures approach in the dynamic analysis of continuous beams under moving oscillators V. De Salvo, G. Muscolino & A. Palmeri

608

Improvement of seismic analysis concerning the characteristic difference of HDR-S between the stages of design and inspection H. Yosuhisa, M.-S. Yoo, D.-H. Ha & K.-Y. Kim

610

Vulnerability assessment of an existing highway bridge by 3-D nonlinear time history analyses and proposing its retrofit design M. Hosseini & S.R. Khavari

611

Shake table studies of scaled reinforced concrete bridge piers subjected near-fault ground motions Y.-S. Chung, C.-Y. Park, H.-K. Hong, D.-H. Lee & C.-S. Shim

612

Computer wind investigations for long bridge crossings D. Janjic & A. Domaingo

613

Identification of the dynamic characteristics of long span bridges using ambient vibration measurements A.L. Hong & R. Betti

614

Application of indexing and detailed seismic risk assessment approaches to existing bridges D. Cardone, G. Perrone & L. Pardi

615

XXVIII

Effectiveness of rupture controllable steel side blocks for elevated girder bridges with isolation bearings N. Asada, M. Matsumura, T. Kitada, M. Sakaida & M. Yoshida

617

Influence of bullet train as dynamic system on seismic performance of Shinkansen viaducts M. Kawatani, X. He, K. Shinagawa & S. Nishiyama

620

Vibration-based tension identification of ultra long stay cables J. Liu, N. Fang & Q. Zhang

623

Calculation of the influence line of a bridge using a moving vehicle A. González & E.J. OBrien

624

Seismic assessment and evaluation of 520 highway bridges in Western Kentucky C.C. Choo, I.E. Harik, W. Zatar & H.S. Ding

625

Cross-sectional stress distribution of short suspenders in arch bridges Y.B. Li & Q.W. Zhang

626

Experimental investigation on the Bi-lateral seismic behavior of a two-span bridge model isolated by rolling-type bearings K.-C. Chang, M.-H. Tsai & Z.-Y. Lin

627

Modal analysis of corrugated steel flexible shell bridge structure before backfilling D. Beben & Z. Manko

628

Experimental study on the shear characteristics of seismic isolation bearings I.J. Kwahk, C.B. Cho & Y.J. Kim

629

Seismic design and performance issues for highway bridges Post-earthquake evaluation of reinforced concrete bridge columns A. Vosooghi, M. Saiidi & S. El-Azazy Identification of effective seismic retrofits for common bridge classes on the basis of failure probability J.E. Padgett & R. DesRoches

633

634

Enhancement of axial ductility of circular concrete bridge columns L.A. Marvel, J.C. West & R.A. Hindi

635

Retrofitting structures with a combination of seismic isolation and attenuation A. Caner, M.J. Abrahams, E. Dogan & C. Ozkaya

636

Supplemental device to improve the performance of seismic-isolated bridges in near-fault zones M. Dicleli

638

Smart sensing and monitoring technologies for bridge maintenance, safety and management Baseline knowledge discovery from one-year structural monitoring measurements of Donghai Bridge Z. Sun, Z.H. Min & Z.F. Zhou XXIX

641

Test-bed implementation of piezopaint-based acoustic emission sensor for crack initiation monitoring Y. Zhang & X. Li

643

Development of experimental benchmark problems for international collaboration in structural response control C.-H. Loh, A.K. Agrawal, J.P. Lynch & J.N. Yang

644

Advance sensor technologies on Korean Bridges: Field benchmark opportunities J.P. Lynch, J.H. Kim, Y. Zhang, M. Wang, H. Sohn & C.B. Yun Remotely controllable structural health monitoring systems for bridges using 3.5 generation mobile telecommunication technology K.Y. Koo, J.Y. Hong, H.J. Park & C.B. Yun Structural damage assessment using optical Fiber Bragg Grating vibration sensing system R.J. Sun, Z. Sun & L.M. Sun

645

646 647

Self-sensing and power harvesting carbon nanotube-composites based on piezoelectric polymers K.J. Loh, J. Kim & J.P. Lynch

648

A nonlinear impedance method and its potential application in baseline free crack detection in metallic structures D. Dutta & H. Sohn

649

Piezoelectric sensor system for structural health monitoring B. Kim & Y. Roh

650

Fatigue reliability updating through inspections and monitoring data of steel bridges C. Wang, X. Yu, Y. Feng & X. Liu

651

Advanced signal processing for ultrasonic structural monitoring of waveguides M. Cammarata, P. Rizzo, D. Dutta, H. Sohn & K.A. Harries

652

Development of an optical fiber corrosion sensors based on light reflection H. Huang & N. Gupta

653

Stochastic Subspace Identification (SSI) model analysis using wireless data logger system in grand bridge under wind load effect Y.-S. Kim, S.-Y. Park, C.-B. Yun & J.-S. Choi

655

Sequential health monitoring in steel plate-girder bridges by using combined vibration-impedance signatures D.S. Hong, J.H. Park, J.T. Kim & W.B. Na

656

Smart bearings for structural behavior monitoring F.M. Wegian, G. Fu, J. Feng, Y. Zhuang & P.-J. Chun

657

Smart structural elements for the condition monitoring of bridge structures D. Zonta, M. Pozzi, H.Y. Wu & D. Inaudi

658

Sensing capability of electromagnetic induction system for vibration control of structures H.J. Jung, D.D. Jang, H.J. Lee, S.W. Cho & J.H. Koo

659

Special session on Incheon bridge Incheon Bridge project outline J.H. Yang Son, M.G. Yun, H.S. Kim, H.Y. Shin & I.S. Shim XXX

663

Design and construction of approach bridge in Incheon Bridge project J.-Y. Song, K.-Y. Choi, H.-Y. Shin, W.-S. Lee, B.-C. Cho & D.-W. Hwang Development of geometry control system for cable-stayed bridges and application to the Incheon Bridge K. Jung & H.S. Lee

665

667

Seismic design and performance assessment of pile-bents in Incheon Bridge viaduct H.-S. Son, M.-S. Oh, K.-L. Park & J.-H. Yang

668

Geometry control for the concrete pylon of Incheon Cable Stayed Bridge D.K. Im, J.G. Yoo, C.H. Kim & H.S. Kim

669

Case study of Osterberg-Cell pile load test on large diameter drilled shaft in Incheon Bridge project S.-H. Shin, Y.-K. Lee, Z.-C. Kim, J.-H. Kim & H.-G. Lee Design of ship impact protection in Incheon Bridge J.H. Kim, H.Y. Shin, H.T. Kim & S.H. Lee

670 671

Structural health monitoring on cable supported bridges Development of bridge WIM systems without axle detector using artificial neural network M.-S. Park, J. Lee, B.-W. Jo & S. Kim

675

Development of local live load truck model for long span bridges based on BWIM data of Seohae cable-stayed bridge M.-S. Park, C.-H. Park & J. Lee

676

Long-term structural behaviors of Seohae cable-stayed bridge based on results from SHM and surveys J.C. Park, C.M. Park, M.S. Park, I.K. Lee & B.W. Jo

678

Modal parameter extraction of Seohae cable-stayed bridge using TDD technique B.H. Kim, J.C. Park, M.S. Park & I.K. Lee

679

Analysis model updating of the Seohae cable-stayed bridge H.K. Kim, S.D. Park, K.T. Kim, W. Park, S.H. Lee, J.F. Choo, J.C. Park & M.S. Park

680

Development of prediction method of non-linear observed data from cable-stayed bridge using support vector regression M.-Y. Park, H.-N. Cho, K.-W. Park, J.-C. Park, M.-S. Park & I.-K. Lee SHMS and wind engineering on the Busan-Geoje Fixed Link bridges Y.M. Kim, D.Y. Kim, C.H. Kim, A. Galmarini, P.D. Frederiksen & J.E. Andersen

681 684

Structural robustness Robustness investigation of long suspension bridges F. Bontempi & L. Giuliani

687

Dynamic analysis for structural robustness evaluation L. Giuliani & F. Bontempi

688

Measure of structural robustness under damage propagation F. Biondini & S. Restelli

689

XXXI

Robustness assessment of a cable-stayed bridge M. Wolff & U. Starossek

690

Approaches to measures of structural robustness U. Starossek & M. Haberland

691

Collapse resistance and robustness of bridges U. Starossek

692

Evaluation of the dynamic amplification factor for cable breakage in cable-stayed bridges Y. Park, H.-M. Koh, J.F. Choo, H. Kim & J. Lee

693

Sustainable bridges Test of a concrete bridge in Sweden. – I. Assessment methods A. Puurula, O. Enochsson, H. Thun, B. Täljsten, L. Elfgren, J. Olofsson & B. Paulsson Test of a concrete bridge in Sweden. – II. CFRP strengthening and structural health monitoring B. Täljsten, M. Bergström, H. Nordin, O. Enochsson & L. Elfgren Test of a concrete bridge in Sweden. – III. Ultimate Capacity O. Enochsson, A. Puurula, H. Thun, L. Elfgren, B. Täljsten, J. Olofsson & B. Paulsson Test to failure of a railway reinforced concrete through bridge in Örnsköldsvik, Sweden. – IV. Evaluation of damage detection methods P.J.S. Cruz & R. Salgado Assessment and monitoring of an old railway steel truss bridge in northern Sweden O. Enochsson, L. Elfgren, A. Kronborg & B. Paulsson Railway bridge loaded to failure test in Örnsköldsvik, Sweden – Strain measurement using Fiber Bragg Grating system incorporated in Carbon Fibre Reinforced Polymer A. Kerrouche, J. Leighton & W.J.O. Boyle

697

698 699

700 701

702

Single and multiple crack monitoring in concrete bridges P.J.S. Cruz, A. Diaz de León & C.K.Y. Leung

704

Structural assessment of concrete railway bridges ˇ M. Plos, K. Gylltoft, K. Lundgren, L. Elfgren, J. Cervenka, A. Herwig, E. Brühwiler, S. Thelandersson & E. Rosell

705

Safety requirements in the capacity assessment of existing bridges J.R. Casas & D.F. Wisniewski

707

Guideline for load and resistance assessment of existing European railway bridges J.S. Jensen, M. Plos, J.R. Casas, C. Cremona, R. Karoumi, & C. Melbourne

708

Improved assessment methods for static and fatigue resistance of old metal railway bridges C. Cremona, A. Patron, S. Hoehler, B. Eichler, B. Johansson & T. Larsson

710

Consideration of dynamic traffic action effects on existing bridges at ultimate limit state E. Brühwiler & A. Herwig

712

XXXII

High cycle fatigue strength of brick masonry. A probabilistic approach J.R. Casas

714

Probabilistic models for resistance of European concrete railway bridges J.R. Casas & D.F. Wisniewski

715

Probabilistic models of material properties for design and assessment of concrete bridges D.F. Wisniewski, P.J.S. Cruz, A.A.R. Henriques & R.A.D. Simões

716

Safety assessment of railway bridges by non-linear and probabilistic methods ˇ ˇ J. Cervenka, V. Cervenka, Z. Janda & R. Pukl

718

Complex multi-tool inspection of a masonry arch bridge using non-destructive testing R. Helmerich, E. Niederleithinger, C. Trela, J. Bien & G. Bernardini

719

Evaluation of corrosion situation on reinforced concrete by portable electrochemical technique R. Bäßler, A. Burkert & T. Frølund Assessment of a railway concrete arch bridge by numerical modelling and measurements G. He, Z. Zou, O. Enochsson, A. Bennitz, L. Elfgren, A. Kronborg, B. Töyrä & B. Paulsson

721

722

Field test – strengthening and monitoring of the Frövi Bridge A. Kerrouche, W.J.O. Boyle, Y. Gebremichael, L. Alwis, K.T.V. Grattan, B. Täljsten & A. Bernnitz

723

Author index

725

XXXIII

Bridge Maintenance, Safety, Management, Health Monitoring and Informatics – Koh & Frangopol (eds) © 2008 Taylor & Francis Group, London, ISBN 978-0-415-46844-2

Preface

The number of deteriorating bridges is increasing worldwide. Costs of maintenance, repair and rehabilitation of these bridges far exceed available budgets. Maintaining the safety of existing bridges by making better use of available resources is a major concern for bridge management. Internationally, the bridge engineering profession has taken positive steps to develop more comprehensive bridge management. It was therefore considered appropriate to bring together all of the very best work that has been done in the field of bridge maintenance, safety, management, lifecycle performance, health monitoring, informatics and cost at the Fourth International Conference on Bridge Maintenance, Safety and Management (IABMAS’08), held in Seoul, Korea from July 13 to 17, 2008. The First (IABMAS’02), Second (IABMAS’04) and Third (IABMAS’06) International Conferences on Bridge Maintenance, Safety and Management were held in Barcelona, Spain, July 14–17, 2002, Kyoto, Japan, October 18–22, 2004, and Porto, Portugal, July 16–19, 2006, respectively. The International Association for Bridge Maintenance and Safety (IABMAS), which serves as the organizing association of IABMAS’08, encompasses all aspects of bridge maintenance, safety and management. Specifically, it deals with : health monitoring and inspection of bridges; bridge repair and rehabilitation issues; bridge management systems; needs of bridge owners, financial planning, whole life costing and investment for the future; bridge related safety and risk issues and economic and other implications. The objective of IABMAS is to promote international cooperation in the fields of bridge maintenance, safety, management, life-cycle performance and cost for the purpose of enhancing the welfare of society. The interest of the international bridge community in all these fields has been confirmed by the high response to the call for papers. In fact, more than 660 abstracts were received at the Conference Secretariat. About 70% of them were selected for final publication as full-papers and presentation at the Conference within four plenary sessions and 72 technical sessions. Compared to IABMAS’06 the total of number of papers scheduled for presentation has increased from 421 to 465. IABMAS’08 covered all major aspects of bridge maintenance, safety, management, health monitoring and informatics including advanced materials, ageing of bridges, assessment and evaluation, bridge codes, bridge diagnostics, bridge management systems, composites, design for durability, deterioration modeling, emerging technologies, fatigue, field testing, financial planning, health monitoring, high performance materials, innovations, inspection, life-cycle performance, load capacity assessment, loads, maintenance strategies, new technical and material concepts, nondestructive testing, optimization strategies, prediction of future traffic demands, rehabilitation, reliability and risk management, repair, replacement, residual service life, safety and serviceability, service life prediction, strengthening, sustainable materials for bridges, sustainable bridges, informatics, and whole-life costing, among others. Bridge Maintenance, Safety, Management, Health Monitoring and Informatics contains the lectures and papers presented at IABMAS’08. It consists of a book of abstracts and a CD-ROM containing the full texts of the lectures and papers presented at IABMAS’08, including the T.Y. Lin Lecture, eight Keynote Lectures and 456 technical papers from 32 countries. This set provides both and up-to-date overview of the field of bridge engineering and significant contributions to the process of making more rational decisions in bridge maintenance, safety, management, life-cycle performance, and cost for the purpose of enhancing the welfare of society. On behalf of IABMAS, the chairs of the Conference would like to take this opportunity to express their sincere thanks to the authors, organizers of special sessions and mini-symposia, and participants for their contributions, to the members of the Conference Scientific Committee for XXXV

their dedicated work, and to the members of the Local Advisory and Organizing Committees for the time and effort they have devoted to making IABMAS’08 a successful event. Finally, we would like to register our sincere thanks to all the sponsors of IABMAS’08. Hyun-Moo Koh and Dan M. Frangopol Chairs, IABMAS’08 Seoul and Bethlehem, April 2008

XXXVI

Bridge Maintenance, Safety, Management, Health Monitoring and Informatics – Koh & Frangopol (eds) © 2008 Taylor & Francis Group, London, ISBN 978-0-415-46844-2

Conference organization

ORGANIZING ASSOCIATION The International Association for Bridge Maintenance and Safety (IABMAS) (http://www.iabmas.org/)

CONFERENCE CHAIRS Hyun-Moo Koh, Seoul National University, Seoul, Korea Dan M. Frangopol, Lehigh University, Bethlehem, PA, USA

HONORARY CHAIR Sung-Pil Chang, Seoul National University, Seoul, Korea

HOST ASSOCIATION Korea Bridge Design & Engineering Research Center, Seoul National University, Korea Under the auspices of Ministry of Land, Transportation and Maritime Affairs, Korea Seoul Metropolitan Government, Korea Korea Institute of Construction & Transportation Technology Evaluation and Planning, Korea Korea Expressway Corporation, Korea Korea Infrastructure Safety & Technology Corporation, Korea Korea Institute of Construction Technology, Korea

CONFERENCE SCIENTIFIC COMMITTEE Joan Casas (Co-Chair) Young Soo Chung (Co-Chair) Andrzej Nowak (Co-Chair) Emin Aktan Alfredo H-S. Ang Giuliano Augusti György L. Balázs Konrad Bergmeister Jan Bien Fabio Biondini John Bjerrum Franco Bontempi

Technical University of Catalonia, Barcelona, Spain Chung-Ang University, Seoul, Korea University of Nebraska, Lincoln, NE, USA Drexel University, Philadelphia, PA, USA University of California, Irvine, CA, USA University of Rome La Sapienza, Rome, Italy Budapest University of Technology and Economics, Budapest, Hungary University of Natural Resources and Applied Life Sciences, Vienna, Austria Wroclaw University of Technology, Wroclaw, Poland Politecnico di Milano, Milan, Italy Danish Road Directorate, Copenhagen, Denmark University of Rome La Sapienza, Rome, Italy XXXVII

Fernando Branco Eugen Bruehwiler Christian Bucher Necati Catbas Michael Chajes Kuo-Chun Chang Sung-Pil Chang (Ex-Officio) Steven Chase Moe Cheung

Technical University of Lisbon, Lisbon, Portugal EPFL, Lausanne, Switzerland Vienna University of Technology, Vienna, Austria University of Central Florida, Orlando, FL, USA University of Delaware, Newark, DE, USA National Taiwan University, Taipei, Taiwan, R.O.C. Seoul National University, Seoul, Korea Federal Highway Administration, McLean, VA, USA The Hong Kong University of Science & Technology, Hong Kong, P.R.C. Hyo-Nam Cho Hanyang University, Ansan, Korea Marios Chryssanthopoulos University of Surrey, Guilford, Surrey, UK Marcello Ciampoli University of Rome La Sapienza, Rome, Italy Joel Conte University of California, San Diego, CA, USA Ross Corotis University of Colorado, Boulder, CO, USA Christian Cremona LCPC, Paris, France Paulo Cruz University of Minho, Guimarães, Portugal Lennart Elfgren Luleå University of Technology, Luleå, Sweden Bruce Ellingwood Georgia Institute of Technology, Atlanta, GA, USA Ib Enevoldsen RAMBOLL, Copenhagen, Denmark Allen Estes California Polytechnic State University, San Luis Obispo, CA, USA Glauco Feltrin Swiss Federal Laboratories for Materials Testing and Research(EMPA), Dübendorf, Switzerland João Almeida Fernandes National Civil Engineering Laboratory, Lisbon, Portugal Joaquim Figueiras University of Porto, Porto, Portugal John Fisher Lehigh University, Bethlehem, PA, USA Michael Forde University of Edinburgh, Edinburgh, UK Dan M. Frangopol (Ex-Officio) Lehigh University, Bethlehem, PA, USA Ian M. Friedland Federal Highway Administration, Washington, DC, USA Yozo Fujino University of Tokyo, Tokyo, Japan Hitoshi Furuta Kansai University, Takatsuki, Japan Yaojun Ge Tongji University, Shanghai, China Hamid Ghasemi Federal Highway Administration, USA Michel Ghosn City University of New York, NY, USA Paul Grundy Monash University, Victoria, Australia Rade Hajdin Infrastructure Management Consultants GmbH, Zürich, Switzerland Geir Horrigmoe NORUT Technology, Narvik, Norway Michael C. H. Hui Government of Hong Kong Special Administrative, Hong Kong, P.R.C. Naeem Hussain ARUP, Hong Kong, P.R.C. Daniele Inaudi SMARTEC SA, Manno, Switzerland Jens Sandager Jensen COWI A/S, Lyngby, Denmark Ahsan Kareem University of Notre Dame, Notre Dame, IN, USA Maria Kaszynska Szczecin Technical University, Szczecin, Poland Malcolm Kerley Virginia Department of Transportation, Richmond, VA, USA Sungkon Kim Seoul National University of Technology, Seoul, Korea Sang-Hyo Kim Yonsei University, Seoul, Korea Risto Kiviluoma WSP Finland Ltd., Helsinki, Finland Wayne Klaiber Iowa State University, Ames, IA, USA Leo Klatter Public Works and Water Management, Utrecht, The Netherlands C.G. Koh National University of Singapore, Singapore XXXVIII

Hyun-Moo Koh (Ex-Officio) Ulrike Kuhlmann John Lane Jørn Lauridsen Hakeun Lee Aiquin Li Chin-Hsiung Loh Giorgio Malerba Ayaz Malik René Maquoi Barney Martin Sami Masri Ayaho Miyamoto Aftab Mufti Hani Nassif Jan M. van Noortwijk Jinping Ou Tso-Chien Pan Livia Pardi Udo Peil Stephen Pessiki Victor Popa Mark Reno James Ricles Salvatore Russo Mehdi Saiidi Richard Sause Robert Sexsmith Richard Shepard Dong-Ku Shin Hyun-Mock Shin Soobong Shin Arunprakash M. Shirole Jongsung Sim Marja-Kaarina Söderqvist Mark Stewart Luc Taerwe Man-Chung Tang Palle Thoft-Christensen Paul Thompson Tomoaki Utsunomiya Pedro Vellasco Thomas Vogel Eiichi Watanabe Zhishen Wu Kentaro Yamada Chung-Bang Yun Riccardo Zandonini Yunfeng Zhang

Seoul National University, Seoul, Korea University of Stuttgart, Stuttgart, Germany Railway Safety and Standards Board, London, UK Danish Road Directorate, Copenhagen, Denmark Korea University, Seoul, Korea Southeast University, Nanjing, China National Taiwan University, Taipei, Taiwan, R.O.C. Politecnico di Milano, Milan, Italy Rensselaer Polytechnic Institute, Troy, NY, USA University of Liège, Liège, Belgium Modjeski & Masters, Poughkeepsie, NY, USA University of Southern California, Los Angeles, CA, USA Yamaguchi University, Ube, Japan ISIS Canada, Research Network, Winnipeg, Manitoba, Canada The State University of New Jersey, New Jersey, USA HKV Consultants, Lelystad, The Netherlands Dalian University of Technology, Dalian, China Nanyang Technological University, Nanyang, Singapore Autostrade per l’Italia, Rome, Italy Technical University of Braunschweig, Braunschweig, Germany Lehigh University, Bethlehem, PA, USA Search Corporation, Bucharest, Romania Quincy Engineering Inc., Sacramento, CA, USA Lehigh University, Bethlehem, PA, USA University Iuav of Venice, Venice, Italy University of Nevada, Reno, NV, USA Lehigh University, Bethlehem, PA, USA University of British Columbia, Vancouver, Canada County of Eldorado, Department of Transportation, Placerville, CA, USA Myongji University, Gyeonggido, Korea Sungkyunkwan University, Gyeonggido, Korea Inha University, Incheon, Korea Arora and Associates, P.C., Minneapolis, MN, USA Hanyang University, Ansan, Korea Finnish Road Administration, Helsinki, Finland University of Newcastle, Newcastle, Australia University of Ghent, Ghent, Belgium T.Y. Lin International, San Francisco, CA, USA Aalborg University, Aalborg, Denmark Castle Rock, CO, USA Kyoto University, Kyoto, Japan State University of Rio de Janeiro, Rio de Janeiro, Brazil ETH Zürich, Zürich, Switzerland Kyoto University, Kyoto, Japan Ibaraki University, Hitachi, Japan Nagoya University, Nagoya, Japan Korea Advanced Institute of Science and Technology, Daejon, Korea University of Trento, Trento, Italy Lehigh University, Bethlehem, PA, USA

XXXIX

CONFERENCE LOCAL ORGANIZING COMMITTEE Young Suk Park (Chair) Hae Sung Lee (Vice-Chair) Jeeho Lee (Secretary) Doobyong Bae Jae-Yeol Cho Dong Ho Choi Dong-Ho Ha Chul-Young Kim Ho-Kyung Kim Jee Sang Kim Jeonghwan Kim Jeong-Tae Kim Nam-Sik Kim Youngjin Kim Jung Sik Kong Sang-Cheol Lee Jae Hoon Lee Yun Mook Lim Chan Min Park Jaegyun Park Jang Ho Park Kwan-Soon Park Seon Kyu Park Young Ha Park Chang Su Shim Won-Sup Hwang Seok-Goo Youn

Myongji University, Gyeonggido, Korea Seoul National University, Seoul, Korea Dongguk University, Seoul, Korea Kookmin University, Seoul, Korea Seoul National University, Seoul, Korea Hanyang University, Seoul, Korea Konkuk University, Seoul, Korea Myongji University, Gyeonggido, Korea Mokpo University, Jeonnam, Korea Seokyong University, Seoul, Korea Samsung C&T Corporation, Seoul, Korea Pukyong National University, Busan, Korea Pusan University, Busan, Korea Korea Institute of Construction Technology, Gyeonggido, Korea Korea University, Seoul, Korea Korea Infrastructure Safety & Technology Corporation, Gyeonggido, Korea Yeungnam University, Gyeongsangbukdo, Korea Yonsei University, Seoul, Korea Korea Expressway Corporation, Gyeonggido, Korea Dankook University, Gyeonggido, Korea Ajou University, Suwon, Korea Dongguk University, Seoul, Korea Sungkyunkwan University, Gyeonggido, Korea Korea Expressway Corporation, Gyeonggido, Korea Chung-Ang University, Gyeonggido Korea Inha University, Incheon, Korea Seoul National University of Technology, Seoul, Korea

CONFERENCE LOCAL ADVISORY COMMITTEE Chang Se Kim (Chair) Won Joong Kim (Secretariat) Woo Jong Kim (Secretariat) Yoon Chul Chun Chun Yang Jung Kyoung Sup Jung Byung Suk Kim Dae-Young Kim Il-Gon Kim Sun Won Kim Sung-Hwan Kim Woo Kim Young-Bong Kwon

Korea Institute of Construction & Transportation Technology Evaluation and Planning, Gyeonggido, Korea Korea Institute of Construction & Transportation Technology Evaluation and Planning, Gyeonggido, Korea DM Engineering Co., Ltd., Seoul, Korea Samsung C&T Corporation, Seoul, Korea Shinsung Engineering Co., Ltd., Seoul, Korea Chungbuk National University, Chungbuk, Korea Korea Institute of Construction Technology, Gyeonggido, Korea Korea Railroad Technical Corporation, Seoul, Korea Korea Infrastructure Safety & Technology Corporation, Gyeonggido, Korea BnS Engineering Co., Ltd., Seoul, Korea Korea Expressway Corporation, Gyeonggido, Korea Chonnam National University, Gwangju, Korea Yeungnam University, Gyeongsangbukdo, Korea XL

Chul Soo Lee Doo Hwa Lee Guem-Sook Lee Hae Kyung Lee Kil Yong Lee Myeong-Jae Lee Sung Chul Lee Sung Min Lee Sung Woo Lee Kyung Kook Lim Hyung-Ghee Park Dong Ho Yoo DukHee Yoo Jae So Yoo Tae Yang Yoon

Chungsuk Engineering Co., Ltd., Seoul, Korea Sambo Engineering Co., Ltd., Seoul, Korea Yongma Engineering Co., Ltd., Seoul, Korea Dasan Consultants Co., Ltd., Seoul Korea Korea Consultant International Co., Ltd., Seoul, Korea Yooshin Engineering Corporation, Seoul, Korea Dongguk University, Seoul, Korea Saman Engineering Co., Ltd., Gyeonggido, Korea Kookmin University, Seoul, Korea Ministry of Land, Transportation and Maritime Affairs, Gyeonggido, Korea University of Inchoen, Incheon, Korea ENVICO Consultants Co., Ltd., Seoul, Korea Seoyeong Engineering Co., Ltd., Seoul, Korea Dohwa Consulting Engineering Co., Ltd., Seoul, Korea Research Institute of Industrial Science & Technology, Gyeonggido, Korea

IABMAS’08 SPECIAL SESSIONS – – – – – – – – – – – – – – – – –

Assessment and control of bridge vibrations, organized by Álvaro Cunha Bridge 200 toward durable bridge, organized by Byung Suk Kim Bridges for high-speed railways, organized by Rui Calçada Damage assessment of existing bridges, organized by Soobong Shin and Jeong Tae Kim Design expectations, monitoring response and maintenance decisions, organized by Giorgio Malerba Development of the advanced robot systems for bridge inspection and monitoring, organized by Jong Seh Lee and Sungkon Kim Fiber reinforced composites in bridges, organized by Sung Woo Lee Integrated assessment – Practical application of probabilistic methods, organized by Alan O’Connor and Jens Sandager Jensen Life-cycle structural engineering, organized by Fabio Biondini Lifetime-perspective design of Kwangyang suspension bridge with main span 1545m, organized by Soon-Duck Kwon and Jaehong Kim New developments in large-scale model studies of bridge components and systems subjected to earthquakes, organized by Mehdi Saiidi Practical application of BMS and BMS-DB, organized by Ayaho Miyamoto and X. Shao Practical applications of SHM techniques for railway systems, organized by Soobong Shin and Jeong Tae Kim Seismic design and performance issues for highway bridges, organized by Murat Dicleli Special session on Incheon bridge, organized by Jae-Yeol Cho and Hyun-Yang Shin Structural health monitoring on cable supported bridges, organized by Chan Min Park Structural robustness, organized by Franco Bontempi and Uwe Starossek

IABMAS’08 MINI-SYMPOSIA – Information technology for lifetime management of bridge, organized by Sang-Ho Lee, Ayaho Miyamoto, Risto Kiviluoma and Jerome P. Lynch – Integrating health monitoring and lifecycle management of bridge and highways, organized by Emin Aktan, Xiaolin Meng, Leo Klatter, Hitoshi Furuta, and Hae Sung Lee XLI

– Monitoring and assessment of bridges using novel techniques, organized by Alfred Strauss and Dan M. Frangopol – Research & applications for bridge health monitoring, organized by Necati Catbas, Joan Casas, and Hitoshi Furuta – Smart sensing and monitoring technologies for bridge maintenance, safety and management, organized by Chung-Bang Yun and Hoon Sohn – Sustainable bridges, organized by Paulo Cruz, Lennart Elfgren and Jens Sandager Jensen

XLII

CONFERENCE SPONSORS (as of April 1, 2008) MAIN SPONSOR Samsung C&T Corporation, Korea

SPONSORS AP – Bridge Construction Systems, Portugal ASCE-SEI, American Society of Civil Engineers – Structural Engineering Institute, USA ASCP, The Portuguese Group of IABMAS, Portugal ASSISi, Anti-Seismic System International Society, Italy ATLSS, Center for Advanced Technology for Large Structural Systems, Lehigh University, USA Betar, Betar Consultores, Lda, Portugal CAU, Chung-Ang University, Korea CERIC, Civil Engineering Research Information Center, Korea COSEIK, Computational Structural Engineering Institute of Korea, Korea COWI A/S, Denmark CU, University of Colorado at Boulder, USA DGU, Dongguk University, Korea ECCS, European Convention for Constructional Steelwork, Belgium IABSE, The International Association for Bridge and Structural Engineering, Switzerland FHWA, Federal Highway Administration, USA JSCE, Japan Society of Civil Engineers, Japan JSMS, The Society of Materials Science, Japan JSSC, Japanese Society of Steel Construction, Japan KBRC, Korea Bridge Design & Engineering Research Center, Korea KCI, Korean Concrete Institute, Korea KEC, Korea Expressway Corporation, Korea KICT, Korea Institute of Construction Technology, Korea KICTEP, Korea Institute of Construction & Transportation Technology Evaluation and Planning, Korea KISTEC, Korea Infrastructure Safety & Technology Corporation, Korea KG-IABSE, Korean Group of IABSE, Korea KSCE, Korean Society of Civil Engineers, Korea KSSC, Korean Society of Steel Constructions, Korea KU, Kansai University, Japan KU-CER, Department of Civil and Earth Resources Engineering, Kyoto University, Japan MJU, Myongji University, Korea MLTM, Ministry of Land, Transportation and Maritime Affairs, Korea NCREE, National Center for Research on Earthquake Engineering, Taiwan, R.O.C OZ – DiagnOstico, levantamento e Controlo de Qualidade, Portugal RCEAS, P.C. Rossin College of Engineering and Applied Science, Lehigh University, USA SEOUL, Seoul Metropolitan Government, Korea SISTeC, Smart Infra-Structure Technology Center, KAIST, Korea SNU, Seoul National University, Korea TRB, Transportation Research Board, USA XLIII

T.Y. Lin, T.Y. Lin International, San Francisco, USA UM, University of Minho, Guimaraes, Portugal UniS, University of Surrey, Guilford, UK UPC, Technical University of Catalonia, Barcelona, Spain

XLIV

TECHNICAL EXHIBITION PARTICIPANTS Bridge Inspection Robot Development Interface (BIRDI), Korea Cervenka Consulting, The Czech Republic/CNG Softtek Co., Ltd., Korea Daelim Industrial Co., Ltd., Korea Daewoo Engineering & Construction/Busan Geoje Fixed Link Corporation, Korea Fixon Inc., Korea Geomonitoring, Korea High Performance Construction Material Research Center, Korea Hyundai Engineering and Construction Co., Ltd., Korea Korea Bridge Design & Engineering Research Center (KBRC), Korea Korea Construction Engineering Development Collaboratory Program (KOCED), Korea Korea Expressway Corporation (KEC), Korea Korea Institute of Construction Technology (KICT), Korea MIDAS Information Technology Co., Ltd., Korea Pure Technologies, USA Pyungsan SI Ltd., Korea Samsung C&T Corporation, Korea Smart Infra-Structure Technology Center (SISTeC)/Infra-Structures Assessment Research Center (ISARC), Korea SK Engineering & Construction Co., Ltd., Korea Strand7 Pty Ltd., Australia/CNG Softtek Co., Ltd., Korea Transpo Industries, Inc., USA

XLV

T. Y. Lin Lecture

Bridge Maintenance, Safety, Management, Health Monitoring and Informatics – Koh & Frangopol (eds) © 2008 Taylor & Francis Group, London, ISBN 978-0-415-46844-2

Fatigue of steel bridge infrastructure J.W. Fisher & S. Roy Center for Advanced Technology for Large Structural Systems, Lehigh University, Bethlehem, PA, USA

ABSTRACT: This paper presents an overview of the development of fatigue design provisions and detailing for steel bridge structures. The historical performance of welded steel bridges in the USA is reviewed with focus on fatigue cracking at cover plate and similar attachment details, as well as distortion induced cracking at web gaps. The role of materials including modern High Performance Steels (HPS) is reviewed. Variable amplitude loading is also examined and compared with current design of steel bridges for fatigue resistance. Also examined are methods to improve and retrofit fatigue sensitive details, including modern post-weld enhancement by Ultrasonic Impact Treatment (UIT). Orthotropic steel decks are reviewed based on the results of two full-scale prototype laboratory fatigue tests which identified the complex behavior that occurs at fatigue sensitive details and were verified by field measurements on field installations. The merits of thin epoxy concrete wearing surfaces is examined in terms of the critical role the deck plate thickness has on the epoxy concrete fatigue resistance and durability. 1 INTRODUCTION Welded and bolted details for bridges are designed based on the nominal stress range that is calculated using mechanics of material equations and does not include the local effect of stress concentrations of welds and attachments. Since fatigue is typically only a serviceability problem, members are designed for fatigue using service loads. It is standard practice in fatigue design of welded structures to separate the weld details into categories having similar fatigue resistance in terms of the nominal stress. Each category of weld details has an associated S-N curve. The S-N curves for steel details in the highway and railway bridge specifications (AASHTO 2004, AREMA 2005) are shown in Figure 1, which are based on a lower bound to a large number of full-scale fatigue

Figure 1. AASHTO design S-N curves.

3

test data with a 97.5% survival limit. Figure 1 also shows the fatigue thresholds or constant amplitude fatigue limits (CAFL) for each category as horizontal dashed lines. When constant amplitude tests are performed at stress ranges below the CAFL, noticeable cracking does not occur. Typically, small-scale specimen tests will result in longer apparent fatigue lives. Therefore, the S-N curve must be based on tests of full size structural components such as girders (Keating & Fisher 1986). Testing on full-scale welded members has indicated that the primary effect of constant amplitude loading can be accounted for in the live-load stress range. The mean stress or the dead load stress is not significant since locally very high residual stresses from welding exist at the weld toe. Cover plate details and equivalent details such as gusset plates are common on older bridges. Hence it is necessary to examine the service loading that bridges are subjected to. 2 VARIABLE-AMPLITUDE FATIGUE All service load histories for bridges consist of stress range cycles of varying amplitudes, hereafter called variable-amplitude (VA) loading. However, the design curves of stress range versus number of cycles, commonly called design S-N curves in the AASHTO LRFD bridge design specifications (2004), are based on fatigue tests that were performed under constant-amplitude (CA) loading. A histogram of VA stress ranges can be converted into an equal number of CA stress ranges that produce the same amount of crack growth as is the case for the VA stress ranges. This so-called equivalent CA stress range is based on Miners rule and given by:

where Sri = the ith stress range in the histogram; φi = frequency of occurrence of Sri ; and 3 is the slope of the log-log linear S-N line for CA fatigue. This equivalent stress range of Sre is referred to as the root-mean-cube (RMC) stress range. When stress ranges in the variable distribution are higher than the CAFL, and have a frequency of 0.05% or more of the cumulative frequency, the equivalent stress range Sre is used with the log-log linear S-N curves the same way as a CA stress range would be used. This design rule is based on the results of long life variable amplitude fatigue tests conducted by Tilly & Nunn (1980) and Fisher et al. (1983, 1993). 3 FATIGUE DESIGN TRUCK The fatigue design truck in the LRFD specifications is based on the design truck, which consists of 35-kN front axle and two 145-kN rear axles. The axle spacings are 4.3 m on the tractor and 9 m on the trailer. Two assumptions were made: (1) the stress range induced at a detail by a truck crossing the bridge is proportional to the gross truck weight; and (2) all trucks crossing the bridge produce the same fatigue damage as is done by an equal number of trucks with axle loads of 75% of the design truck, and axle spacings of 4.3 and 9 m. The equivalent fatigue truck weight was calculated (Moses et al. 1987) analogous to calculating the equivalent stress range of a VA spectrum with Equation 1. A constant axle spacing of 9 m was found to best approximate the axle spacing of typical four and five axle trucks responsible for most fatigue damage to bridges. 4 EXPERIENCE WITH FATIGUE CRACKING Fatigue cracking in steel bridges in the United States has become more frequent in its occurrence since the 1970’s. A large crack was discovered in 1970 at the end of a cover plate in one of the Yellow Mill Pond (YMP) multi-beam structures located at Bridgeport, Connecticut (Fisher 1984). 4

Figure 2. Yellow Mill Pond Bridge: fatigue crack at the end of cover-plate.

Between 1970 and 1981, numerous fatigue cracks were discovered at the ends of cover plates in this bridge as seen in Figure 2. In most cases, fatigue cracking in bridges resulted from an inadequate experimental base and overly optimistic specification provision developed from the experimental data in the 1960’s. The fatigue problems with the older bridges can be avoided in new construction if good detailing practice is followed and each detail is designed such that the stress range due to applied live load is below the design allowable stress range. It is also possible to retrofit or upgrade the fatigue strength of existing steel bridges with poor details. Peening works primarily by inducing a state of compressive residual stress near the weld toe (Fisher et al. 1979). Because the benefit of peening is derived from lowering the effective tensile stress range, it has been found to be most effective when conducted under dead load. In this case, the peening only needs to be effective against live load. Air-hammer peening (AHP) can be a successful repair as long as the crack depth does not exceed the zone of compressive stress. The YMP Bridge structure was retrofitted by peening and gas tungsten arc (GTA) re-melting in the 1970’s. This prevented subsequent crack growth in this heavily used structure until it was replaced in 1997. Subsequently, several beams removed from the original structure were tested in the laboratory (Takamori & Fisher 2000). The tests verified that no fatigue crack growth had occurred in these bridge details after more than 60 million cycles of truck loading and the repairs had successfully prevented further growth at the treated details. At the higher test stress range, the laboratory tests were found to develop fatigue cracks in the weld throat and not at the treated weld toe. 5 DISTORTION-INDUCTED FATIGUE Most cracks found in bridges were caused by distortion of member cross sections and out-of-plane deformations of webs that induced localized bending stresses (Fisher et al. 1990). Out-of-plane distortion occurs mainly at attachment plates for diaphragms, transverse stiffeners and floor beams. The solution to this problem lies in proper detailing that eliminates the secondary stresses. In most cases, problems with web-gap-cracking can be solved by rigidly connecting the attachment plate to the tension flange. In the case where the distortion is limited, holes may be drilled or cored at the crack tips to temporarily arrest propagation (Fisher et al. 1980). Holes essentially blunt the tip of the crack. In cases where the distortion is displacement limited, the stresses can be reduced by increasing the flexibility of the connection. The flexibility may be increased by allowing a small fatigue crack to remain after drilling or coring holes at the crack tips. Another way to increase the flexibility of the joint is to remove part of the stiffener or connection plate and increase the length of the gap. 5

Figure 3.

Retrofitting by connection stiffening.

In case where the distortion is not displacement limited (i.e. load controlled), hole drilling or increasing the flexibility of a connection will not work. In these cases, and even in many displacement limited cases, the best solution to distortion cracking is to increase the rigidity of the connection. In new construction, the bridge specifications now recommend that stiffeners and connection plates should be rigidly connected to both flanges and the web. Figure 3 shows a tee connection bolted to the flange and transverse connection plate in order to “bridge” the web gap. 6 HIGH PERFORMANCE STEELS AND ENHANCEMENT The development of high performance steels such as HPS Grade 485 W and HPS Grade 690 W has shown that without enhancement of welded details their fatigue resistance is no different than other high strength steels in use during the last four decades (Fisher et al. 1970). Post-weld enhancement of fatigue resistance of welded details such as cover-plates, gussets and stiffeners that are known to experience crack growth from a weld toe is essential for an efficient use of these modern high performance steels. As noted in the previous section, peening and gas tungsten arc remelting has been used in the past to improve the fatigue resistance of welded details that have experienced fatigue damage. Over the past decade, ultrasonic impact treatment (UIT) has proved to be a consistent and effective means of improving fatigue strength of welded connections. Research at Lehigh University on large scale specimens having stiffener and cover-plate welded details has demonstrated that substantial increases in fatigue strength of these high strength steel welded details can be achieved by UIT in particular the elevation of their fatigue limit (Roy et al. 2003, Roy & Fisher 2005, 2006). UIT involves post-weld deformation treatment of the weld toe by impacts from single or multiple indenting needles excited at ultrasonic frequency, generating force impulses at the weld toe (Statnikov 1997). The treatment introduces beneficial compressive residual stresses at the weld toe and also reduces the stress concentration by enhancing the profile of the weld toe. The UIT equipment consists of a handheld tool consisting of an ultrasonic transducer, a wave guide, and a holder with impact needles; an electronic control box; and a water pump to cool the system. Compared with traditional impact treatment methods such as air hammer peening, shot peening and needle peening, UIT appears to be more efficient and environmentally acceptable. The large scale beam tests showed that although the treated details suppressed crack growth from the weld toe, when the usual end weld size was used the failure mode changed to fatigue crack growth from the weld root. This usually resulted in a longer life but still led to cracking and failure (Roy et al. 2003, Roy & Fisher 2005). For enhanced fatigue resistance it was desirable to prevent 6

Figure 4.

Design curve for end welded cover-plate details treated by UIT; 0 ≤ R ≤ 0.1.

Figure 5.

Design curve for end welded cover-plate details treated by UIT; 0.1 < R ≤ 0.5.

root cracking and this was achieved by increasing the size of the end weld at the cover-plate to the plate thickness, which reduced the stress concentration at the weld root (Takamori & Fisher 2000). The test results also showed that the enhancement in fatigue resistance was dependent on both the stress range Sr and the minimum stress Smin . Substantial enhancement results when the treatment is applied under a high level of minimum stress. This was verified experimentally for weld toes treated by air hammer peening (Fisher et al. 1979). Design curves for Category E’ end welded cover-plates treated by UIT are provided in Figures 4 & 5. As is apparent in Figure 4, treated details under low minimum stress (i.e. the R-ratio of Smin /Smax is less than 0.1 or the detail treated under dead load) provide a design fatigue limit corresponding to Category B of the AASHTO specifications. None of the end-welded coverplate details developed fatigue cracks below 110 MPa, the CAFL for Category B (Roy & Fisher 2006). When the treatment is applied before the dead load stress, and the R-ratio is bracketed by 0.1 < R < 0.5, the design fatigue limit is decreased as shown in Figure 5 to 70 MPa which is the fatigue limit for Category C. Although there is enhancement in the finite life, it is not as significant as the increase in the fatigue limit for this class of detail. 7

Cover-plate end welds on existing bridges are not likely to have end weld size same as the plate thickness. More likely the weld size will be about half the plate thickness. The test results indicated that when the R-ratio was less than 0.1, the enhanced fatigue resistance was applicable to the weld toe. There is a high probability that fatigue crack growth will initiate at the weld root as was demonstrated in the girders that were removed from the Yellow Mill Pond Bridge that were treated by air hammer peening and gas tungsten arc re-melting (Takamori & Fisher 2000). This would indicate that inspections should focus on the weld throat to ascertain if root cracking would subsequently develop. Fortunately, there is a significant increase in life for root cracking to occur and the cycles (time) necessary for the crack to propagate across the cover-plate end to the longitudinal welds which is the only way the crack can enter into the girder flange. Normal periods of inspection should identify such throat cracking if it ever occurs. 7 ORTHOTROPIC STEEL DECKS During the past decade, full-scale laboratory and field testing of portions of several orthotropic bridge decks have been conducted (Tsakopoulos & Fisher 2003, 2005). These tests were carried out to minimize the possibility of fatigue cracking as orthotropic deck systems in service in Europe, UK, Australia and Japan have exhibited fatigue cracking in various components of the steel deck system including rib to floorbeam (diaphragm) connections and the rib to deck or the diaphragm to deck connection, particularly when the deck plate thickness was less than 14 mm and when fillet welds were used to connect the ribs to the deck plate. Particularly sensitive in the orthotropic deck system is the rib-to-diaphragm connection – the welded connection between the transverse (floorbeam) diaphragm plate and the continuous longitudinal ribs that are being supported. Concern for the fatigue resistance of rib-to-diaphragm connections on the replacement deck panels resulted in the development of alternatives proposed by the consulting firm Steinman, Boynton, Gronquist, and Birdsall for the Williamsburg Bridge (Gajer et al. 1996), and by Weidlinger Associates for the Bronx Whitestone Bridge (Fanjiang et al. 2004). 7.1 Prototype laboratory tests The two independent laboratory fatigue test programs on a prototype and an as-built deck panel of the Williamsburg Bridge (Kaczinski et al. 1997, Tsakopoulos & Fisher 2003), and on the prototype deck panel for the Bronx-Whitestone Bridge were conducted in the multidirectional reaction wall test facility at the Advanced Technology for Large Structural Systems (ATLSS) Engineering Research Center, Lehigh University. The loading configuration represented a single-axle that was consistent with the characteristics of a HS20 design truck axle and the HS15 fatigue truck. This provided a more severe loading condition on the floorbeam diaphragm(s) than if a tandem-axle was used. The laboratory fatigue test programs on full-scale steel orthotropic deck panels for the Williamsburg and Bronx-Whitestone Bridge provided valuable information on the complex behavior and fatigue performance of orthotropic deck systems that was in good agreement with finite element models used for design. The results reflected a capacity inherent to the orthotropic deck system to redistribute stresses induced under the elevated truck loadings that were simulated. The effectiveness of design improvements that ultimately enhanced the fatigue resistance of the replacement deck panels currently in service are expected to exceed the required 75-year design life on both the bridges. 7.2 Results of long term remote monitoring Long-term monitoring of the Williamsburg Bridge began in August of 1998 and continued for seven months (Connor & Fisher 2001). The measurements indicated that the variable amplitude stress range spectrum has a wider band width than assumed in the AASHTO-LRFD bridge design specifications (2004) for the rib-diaphragm cut-out. Similar results were obtained on the BronxWhitestone Bridge (Connor et al. 2003). The field measurement results underscored a need for 8

modifications in the fatigue limit state load in the AASHTO specification for the diaphragm details at the cutout, which should be designed for a fatigue limit state stress range of 3 Sreff . Other elements such as the deck plate-to-rib connection and the floorbeam were observed to satisfy the AASHTO LRFD design fatigue limit state stress range of 2 Sreff . 7.3 Wearing surfaces Various materials have been used and/or tested for wearing surfaces on steel orthotropic-plate bridge decks including Portland cement concretes, asphaltic concretes with or without polymer modification, epoxy concretes, methyl-methacrylate concretes, hybrid epoxy-urethane aggregate surfaces, polyurethane-aggregate surfaces and polyester–sand surfaces. There is considerably more experience with use of these surfacing materials on concrete decks than on orthotropic steel decks. Flexibility of the thin steel deck plate introduces a fatigue loading and other more severe conditions than are present in a concrete deck application. Originally 50 to 70 mm asphaltic concrete surfaces were installed on the orthotropic decks of the Poplar Street Bridge across the Mississippi river in St Louis, MO, the McNaughton Bridge in Peoria, IL and the Champlain Bridge in Quebec between 1960’s and early 1990’s. The second and third asphaltic concrete wearing surfaces installed in the 1980’s on the Poplar Street Bridge were observed to provide poor performance by de-bonding, shoving and rutting, and failed after three and four years of service. All of these structures are also exposed to a wide range of temperature including below freezing. As a part of the 1989–1991 process for selecting a replacement surfacing material for the Poplar Street Bridge, MO, a laboratory test program was carried out at the University of Missouri-Columbia (Gopalaratnam et al. 1989, Gopalaratnam et al. 1999). Concurrently, test panels on the bridge were monitored under normal service conditions. Bridge deck strains were also measured under normal service conditions. In 1992 an epoxy concrete surface was installed on the bridge using the slurry method of application During the first five years of service there were no pop-outs or any other de-laminations of the epoxy concrete overlay from the steel deck. However, longitudinal fatigue cracks were found in the wearing surface at the west and east ends of the bridge over the ribs having crack widths of 1.5 mm to 3 mm. These cracks did not result in de-bonding of the wearing surface until 2003. By 2005 (year 13), some large areas of de-lamination were found in the eastbound lanes. In September 2005, repairs were made to areas where cracks had developed in the T-48 slurry along the trapezoidal rib lines. In 2006, the entire original wearing surface was removed and the deck was resurfaced using the same T-48 epoxy concrete. With its 14 mm thick steel deck plate, fatigue cracking will likely reoccur with a similar service life.

8 CONCLUSION Fatigue of steel bridges under traffic loading is the most significant issue affecting the service performance of aging transportation infrastructure in the USA and in many other countries around the world. Research and case studies of in-service fatigue cracking of steel bridges over the past 40 years have helped in formulating design guidelines and improved detailing practices, implementation of which have limited fatigue cracking in new construction. However, the risk of fatigue fracture of many steel bridges that were built prior to the implementation of the current practices and the economic impact of replacing the deficient bridges remain high. While fatigue fracture limit state in new steel bridges can be suppressed by avoiding the fatigue critical Category D, E or E’ attachments, the performance of these details in existing bridges may be enhanced by weld toe treatments such as air hammer peening, GTA re-melting, or UIT. Post-weld toe treatments should also be considered in new structures for efficient use of modern HPS, where the attachment details cannot be avoided. The orthotropic deck is the only bridge deck system likely to provide a 100 year life when the deck plate thickness equals or exceeds 16 mm. 9

REFERENCES AASHTO 2004. LRFD bridge design specifications. Washington, D.C.: American Association of State Highway and Transportation Officials (AASHTO). AREMA 2005. Manual of railway engineering. Washington, D.C.: American Railway Engineering and Maintenance of Way Association (AREMA). Connor, R.J. & Fisher, J.W. 2001. Results of field measurements on the Williamsburg Bridge orthotropic deck: Final report on Phase III. ATLSS Report No. 01-01. Bethlehem, PA: ATLSS Engineering Research Center, Lehigh University. Connor, R.J., Richards, S.O. & Fisher, J.W. 2003. Long-term monitoring of prototype orthotropic deck panels on the Bronx-Whitestone Bridge for fatigue evaluation. In K.M. Mahmoud (ed.), 2003 NewYork City Bridge Conference; Proc., New York City, October 20–21. Lisse: Swets & Zeitlinger. Fanjiang, G.-N., Ye, Q., Fernandez, O.N. & Taylor, L.R. 2004. Fatigue analysis and design of steel orthotropic deck for Bronx-Whitestone bridge, New York City. Transportation Research Record 1892: 69–77. Fisher, J.W., Frank, K.H., Hirt, M.A. & McNamee, B.M. 1970. Effect of weldments on the fatigue strength of steel beams. NCHRP Report 102. Washington, D.C.: Highway Research Board. Fisher, J.W., Hausammann, H., Sullivan, M.D. & Pense, A.W. 1979. Detection and repair of fatigue damage in welded highway bridges. NCHRP Report 206. Washington, D.C.: Transportation Research Board. Fisher, J.W., Barthelemy, B.M., Mertz, D.R. & Edinger, J.A. 1980. Fatigue behavior of full-scale welded bridge attachments. NCHRP Report 227. Washington, D.C.: Transportation Research Board. Fisher, J.W., Mertz, D.R. & Zhong, A. 1983. Steel bridge members under variable amplitude long life fatigue loading. NCHRP Report 267. Washington, D.C.: Transportation Research Board. Fisher, J.W. 1984. Fatigue and fracture in steel bridges: case studies: John Wiley. Fisher, J.W., Jin, J., Wagner, D.C. & Yen, B.T. 1990. Distortion-induced fatigue cracking in steel bridges. NCHRP Report 336. Washington, D.C.: Transportation Research Board. Fisher, J.W., Nussbaumer, A. & Keating, P.B. 1993. Resistance of Welded Details Under Variable Amplitude Long-Life Fatigue Loading. NCHRP Report 354. Washington, D.C.: Transportation Research Board. Gajer, R.B., Patel, J. & Khazem, D. 1996. Orthotropic steel deck for the Williamsburg bridge reconstruction, 14th Structures Congress; Proc., Vol. 1, Chicago, IL. New York: ASCE. Gopalaratnam, V.S., Baldwin, J.W., Hartnagel, B. & Rigdon, R.A. 1989. Evaluation of wearing surface systems for orthotropic steel-plate bridge decks. MCHRP Report No. MO-FHWA-89-2. Columbia, MO: University of Missouri-Columbia. Gopalaratnam, V.S., Baldwin, J.W. & Cao, W.-M. 1999. Temperature-dependent performance of polymer concrete wearing surface system on the Poplar Street Bridge. Report No. RDT 99-001/RI 90-16. Columbia, MO: University of Missouri-Columbia. Kaczinski, M.R., Stokes, F.E., Lugger, P. & Fisher, J.W. 1997. Williamsburg Bridge orthotropic deck fatigue test. ATLSS Report No. 97-04. Bethlehem, PA: ATLSS Engineering Research Center, Lehigh University. Keating, P. & Fisher, J.W. 1986. Evaluation of fatigue tests and design criteria on welded details. NCHRP Report 286. Washington, D.C.: Transportation Research Board. Moses, F., Schilling, C.G. & Raju, K.S. 1987. Fatigue evaluation procedures for steel bridges. NCHRP Report 299. Washington, D.C.: Transportation Research Board. Roy, S., Fisher, J.W. & Yen, B.T. 2003. Fatigue resistance of welded details enhanced by ultrasonic impact treatment (UIT). International Journal of Fatigue 25(9–11): 1239–1247. Roy, S. & Fisher, J.W. 2005. Enhancing fatigue strength by ultrasonic impact treatment. International Journal of Steel Structures 5(3): 241–252. Roy, S. & Fisher, J.W. 2006. Modified AASHTO design S-N curves for post-weld treated welded details. Journal of Bridge Structures – Assessment, Design and Construction 2(4): 207–222. Statnikov, E.S. 1997. Applications of operational ultrasonic impact treatment (UIT) technologies in production of welded joint.IIW Doc. No. XII-1667–97. Paris: International Institute of Welding. Takamori, H. & Fisher, J.W. 2000. Tests of large girders treated to enhance fatigue strength. Transportation Research Record 1696: 93–99. Tilly, G.P. & Nunn, D.E. 1980. Variable amplitude fatigue in relation to highway bridges. Proceedings of the Institution of Mechanical Engineers (London) 194: 259–267. Tsakopoulos, P.A. & Fisher, J.W. 2003. Full-scale fatigue tests of steel orthotropic decks for the Williamsburg Bridge. Journal of Bridge Engineering 8(5): 323–333. Tsakopoulos, P.A. & Fisher, J.W. 2005. Full-scale fatigue tests of orthotropic deck panel for the BronxWhitestone Bridge rehabilitation. Journal of Bridge Structures – Assessment, Design and Construction 1(1): 55–66.

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Keynote Lectures

Bridge Maintenance, Safety, Management, Health Monitoring and Informatics – Koh & Frangopol (eds) © 2008 Taylor & Francis Group, London, ISBN 978-0-415-46844-2

Managing seismic performance of highway bridges – Evolution in experimental research M. Saiidi University of Nevada at Reno (UNR), Reno, Nevada, USA

ABSTRACT: Earthquakes of the past four decades have revealed the vulnerability of modern bridges to strong seismic events and have pointed out the need for improvements in design and construction. Earthquake and bridge engineering researchers and practitioners have been responsive by investigating the seismic behavior of bridges and developing new seismic design and detailing methods. Because strong earthquakes are relatively rare the waiting time to evaluate new designs in the field is too long and relying exclusively on field evaluation of new designs is impractical. The clear alternative is experimental testing of bridges under simulated seismic loadings. The utilization of experimental testing data to understand and improve the seismic performance of bridge structures is relatively new. Fifty-two years ago at a meeting of world experts and researchers of earthquake engineering, field observation was the only assessment technique that was discussed with respect to verification of design in physical structures, and laboratory tests were not included in any of the article. Many challenges have existed in experimental studies of bridges: (1) for the research results to be credible, the size of bridge models need to be sufficiently large to represent full-scale structure behavior, (2) large-scale bridge models require large and expensive testing facilities and equipment, and (3) the cost of construction, instrumentation, and data interpretation of models is beyond the available research funds. Because of these limitations, experimental studies of bridges were initially very limited. Researchers resorted to relatively small scale models. Furthermore, they focused primarily on bridge components because the facilities and funding would not allow for subsystem or system experimental studies. Fortunately, the challenges have been overcome gradually for a number of reasons that include: (a) increased awareness of the public about the importance of bridges within the highway network and the consequences of bridge failure on the local, regional, national, and, often, on international economy, (b) development of advanced and robust testing and sensor technologies, (c) availability of funds to construct large-scale testing facilities including large shake tables to simulate the dynamic effect of earthquakes. As a result of these changes, seismic experimental studies of bridges have undergone an evolution. The evolutionary path, however, has not been a single one. Rather it has been multiple path encompassing conventional bridges, retrofit studies, innovative details, materials, and systems, and repair studies. The state-of-the-art in different paths has different level of maturity, thus leaving room for considerable future research in bridge earthquake engineering.

Figure 1 shows examples of bridge failures that triggered laboratory research of bridge components. Because of the high cost and long duration of model construction in addition to high cost of laboratory testing, only a limited number of variables can be studied experimentally. As a result laboratory testing has been generally complemented by analytical studies to better interpret the performance of the models, and to develop reliable computer models that may be used for extensive parametric studies. As the public interest in improved seismic performance of bridges expanded over the decades and the available funds for research and facilities increased, researchers were able to switch from 13

Figure 1.

Examples of bridge failure in recent earthquakes.

individual component tests to bridge subsystems incorporating the joints and cap beams. More recently with the establishment of the Network for Earthquake Engineering Simulation (NEES) by the US National Science Foundation and the completion of the Miki E-Defense large shake table system in Japan it has become possible to study larger models subjected to dynamic testing that utilize multiple shake tables. Figures 2 shows the evolution in the complexity and size of the bridge component, subsystem, and complete system models, and Figure 3 shows a large-scale, two-span bridge model to be tested at Miki facilities. Innovation in bridge earthquake engineering has encompassed the use of new devices and new materials. Large isolators used mostly in signature bridges have shown a tremendous benefit in reducing the seismic force demand in bridges. Fiber-reinforced polymer (FRP) fabrics have also found their way in bridge seismic retrofit and repair application. Because these devices and materials are new to civil infrastructure, they have required extensive studies and demonstration of performance in the laboratory environment. Figure 4 provides examples of large isolators and various forms of FRP applications. More innovative materials such as shape memory alloys or columns with built in isolators are being investigated to utilize their property in improving the seismic performance of bridges. With the drive toward accelerated bridge construction more challenging details will be required that would potentially require more innovations in detailing and materials. Figure 5 shows examples of column with built-in isolator and SMA reinforced concrete columns. The full article and the presentation will provide more details of the samples discussed in previous paragraphs and present selected experimental results and their design implications.

14

Figure 2.

Evolution from single-column test to full bridge system test.

Figure 3. Two-span bridge test model to be tested in Miki.

15

Figure 4.

Examples of isolator and FRP application for retrofit and repair.

Figure 5.

Innovative details in column plastic hinge zone.

16

Bridge Maintenance, Safety, Management, Health Monitoring and Informatics – Koh & Frangopol (eds) © 2008 Taylor & Francis Group, London, ISBN 978-0-415-46844-2

Cost-effective and durable cable-stayed bridges H. Svensson Leonhardt, Andrä und Partner, Consulting Engineers, Germany

1 INTRODUCTION All engineered structures are expected to be cost-effective and durable. This is especially true for cable-stayed bridges, which represent a major public investment in infrastructure. Due to their lightness special care has to be taken in this regard. The terms cost-effectiveness and durability are closely connected. In a narrow sense cost-effectiveness can be defined as the lowest possible construction costs. These are determined by competition. The types of competition vary from traditional comprehensive tender where contractors can only bid on one design to design-build competitions where each contractor has to offer his own design. The decisive factor for the outcome of the competition is the price. In build-operate-transfer competition where the competitors have to finance the project themselves, the requested State subsidy or the toll rate may determine the outcome. In a broader sense cost-effectiveness means the life-cycle costs of a bridge. In addition to the construction costs, those for maintaining a bridge over its entire life are equally important i.e. the durability is of overriding concern. For a cable-stayed bridge the most sensitive structural members are the stay cables. Their resistance against corrosion and fatigue determines their useful life. Since cable-stayed bridges are light structures, their durability also depends on their robustness against outside attacks, e.g. against high winds and ship collision. For each characteristic discussed in the following, examples of cable-stayed bridges are given and the involvement by Leonhardt, Andrä und Partner (LAP) is mentioned. 2 COST-EFFECTIVENESS Cost-effectiveness of cable-stayed bridges is considered initially as minimum construction cost which is best proved by bidding results. The bids by the contractors can be made either on a given tender design or on contractor’s own designs. Worldwide various methods exist to determine the most cost-effective design for a given location, which are outlined below. 2.1 Tender designs The classical method in Germany and other countries to determine the lowest cost for a bridge is to tender an official design. This design is usually worked out by a consultant for the client. Contractors are then asked to offer their bid for this design, sometimes including certain small improvements. One typical example is the Elbe River Crossing at Niederwartha in Germany (Fig. 1), a steelcomposite superstructure with a main span of 192 m and one tower only. For the State of Saxony LAP prepared preliminary designs from which a tender design was selected and advertised. Eight groups of contractors offered bids in the range of 12.9 to 15.9 Mio. € . The lowest bidder was awarded the contract. In this particular case LAP also prepared the detailed design and construction engineering for the contractor and supervised the construction on site. 2.2 Contractor’s alternates in germany In Germany the system of so-called contractor’s alternates was introduced already during the 1930s. It means that a contractor may offer his own design in addition to offering the official 17

Figure 1.

Niederwartha Bridge, Germany.

Figure 2.

Rhine River Bridge at Wesel, Germany.

design mentioned under Section 2.1 above. The conditions for contractor’s alternates are carefully outlined in the tender documents. The tender design is basically a preliminary design with estimated quantities, and the contractor is paid for the actually built-in quantities by the unit prices of his original bid. For the contractor’s alternate the contractor has to accept full responsibility for the design and is paid by lump sum. The appropriate quality of the contractor’s alternate is ascertained by an Independent Checking Engineer and close supervision on site. The risk for the contractor is bigger when he makes a lump sum bid for his own alternate. An example for a contractor’s alternate is the Rhine River Bridge at Wesel in Germany (Fig. 2) with a main span of 335 m and one tower only. The outer shape of the bridge could not be changed, however, the contractor with the assistance of LAP proposed important structural improvements e.g. changing the stay cables from locked coil ropes to parallel strands (see Section 3.1), to change the construction of the approach bridge to incremental launching and to relocate the connection between the concrete approach and the steel main span. The contract was awarded on this contractor’s alternate for which LAP executed the detailed design and construction engineering. 2.3 Alternative designs in the US In the US the contractor was traditionally not at all involved in the design of a bridge. A consultant prepared the detailed design on behalf of the client which was bid for contractors and the lowest bidder was awarded the contract. He built the bridge according to plans, but was not responsible whether the completed structure would serve its intended purpose. In the late 1970s the cable-stayed East Huntington Bridge across the Ohio River with a main span of 274 m and one tower only had been designed in steel (Fig. 3) and the main foundations were already completed. In that stage the Federal Highway Administration decided that from now on major bridges should be designed independently both in steel and in concrete, and that the alternate with the lowest bid should be built. In this way design competitions were introduced to the US to overcome the reluctance of US contractors to assume responsibility for their own alternate designs. LAP in association with A. Grant & Associates designed the concrete alternate as light as possible (high strength concrete, steel cross girders) in order to fit onto the existing piers. In competitive bidding the concrete alternate won with a low bid of 23.5 Mio. US$ against the steel alternate with 33.3 Mio. US$ and thus proved to be the more cost-effective alternate. For the Houston Ship Channel Crossing at Baytown (Fred Hartmann Bridge), Texas, (Fig. 4) the alternates were given to the same designers. The composite alternate was designed most costeffective e.g. by using two separate beams with four cable planes to reduce transverse bending and by minimizing the tower wall thicknesses to 30.5 cm by designing them as a truss in transverse direction. This time LAP’s composite alternate won, there were no bids for the concrete alternate. The US procedure of creating competitive bidding without burdening the contractor with the 18

Figure 3.

East Huntington Bridge, WV, USA.

Figure 4. USA.

Houston Ship Channel Crossing, TX,

Figure 5.

Kap Shui Mun Bridge, Hong Kong.

Figure 6.

Geo Geum Bridge, Korea.

responsibility for a design proved to be successful. Another way of reducing costs by so-called “value engineering”, in which savings introduced by the contractor after a job has been awarded to him are split between the client and the contractor did not prove successful. 2.4 Design-Build In most countries of the world bridges are tendered by the so-called “design-build” method. The client does not prepare a tender design but only states his requirements which each design must fulfill. The contractors are then asked to offer their own designs for a lump sum price. In this way the widest variety of bridge systems, contractors’ experience and consultants’ ability are combined to find out the most cost-effective design. Since contractors today do not have comprehensive design offices within their company they commission the design of their alternate to a consultant. The resulting design evolves in discussions between designer and contractor and takes into account the special abilities of the contractor. The contractor has to accept responsibility for the design. The Kap Shui Mun Bridge in Hong Kong forms part of the connection to the new Lantau Airport (Fig. 5). It was the first design-build project in Hong Kong. A Japanese joint venture headed by Kumagai engaged Greiner Engineering with LAP as special bridge consultant. The requirements of road and light rail traffic together with typhoon conditions resulted in a unique composite double deck bridge (Fig. 5, bottom right) with a main span of 430 m. In 2002 the Geo Geum Bridge in South of Korea was tendered by the government as design-build project (Fig. 6). Hyundai Construction engaged Hyundai Engineering with LAP as foreign bridge consultant to develop the design. The cable-stayed bridge with a main span of 480 m carries a truss double deck steel-composite girder with road traffic running on top and bicycle and emergency 19

Figure 7.

Myo Island Bridge, Korea.

Figure 8.

Orinoco II Crossing, Venezuela.

lanes on the bottom flange inside the truss. Out of several bids from different joint ventures this design proved to be most cost-effective. For Lot 1 of the Myo Island Bridge, also in the South of Korea, (Fig. 7) GS Construction engaged Yooshin Engineering with LAP as foreign bridge consultant. In this case a composite steel plate girder was designed for the main span of 430 m which was then selected for construction.The contractor Odebrecht was awarded the Second Orinoco Crossing in Venezuela with a length of 3.6 km and two central cable-stayed bridges back-to-back (Fig. 8). Four lanes of highway traffic and a central railway line are supported by a composite box girder for both main spans of 300 m. Odebrecht hired LAP together with the local consultant Brave for the design and construction engineering. This bridge was completed in 2006. 2.5 Build-operate-transfer (BOT) For very major projects the clients sometimes lack the money to build the bridge and the organization to collect tolls and to manage and maintain the bridge. In this case so-called “build-operate-transfer” projects are tendered in competition between different joint ventures. These usually have to finance the bridge construction, refinance themselves by tolls over about 30 years and then return the bridge in good condition to the client. Therefore, not only the first costs but also the costs for maintenance over 30 years are of importance. This is where the durability of the structure becomes especially important. The outcome of the competition is, therefore, not decided by the price for construction but by the amount of toll or by the required subsidy. In 1998 a joint venture under the contractors Impregilo and HochTief hired LAP as main consultant for the design for a 4.1 km bridge across the Parana River between the cities of Rosario and Victoria in Argentina (Fig. 9). The competition was won by the amount of subsidy requested. The design comprises a central cable-stayed bridge with a main span of 350 m and an open concrete girder built cast-in-place by free-cantilevering. The sea-going ship traffic on the Parana River required independent protections against ship collision, taking into account a possible scour around the pile foundations. The bridge was completed in 2002. When the Ma Chang Bridge in South Korea (Fig. 10) was tendered as a build-operate-transfer project, the joint venture of Hyundai Construction and Bouygues hired Hyundai Engineering with LAP as foreign bridge consultant. Their design was successful, comprising a cable-stayed composite bridge with a main span of 400 m. For the sea-going ships the Ma Chang Bridge is provided with strong foundations to withstand potentially high loadings from vessel collisions. In this case, however, seismic loads are governing. The realization of a major crossing of the Baltic Sea between the German Island of Fehmarn and Denmark has been decided by the Governments of the two countries. The bridge will be 20 km long and is designed as a two level structure with a four lane motorway on top and two railway tracks 20

Figure 9.

Figure 11.

Rosario-Victoria Crossing, Argentina.

Figure 10.

Ma Chang Bridge, Korea.

Fehmarnbelt Crossing, Germany / Denmark.

on the lower level inside the truss girder (Fig. 11). The main bridge has been designed by LAP as a cable-stayed bridge with three main spans of 724 m each. This design is currently considered to be the most economic solution. The tender process will start in 2008 and will probably take the form of BOT. Once completed this will be the longest bridge in Europe. In the times where public funds appear to be lacking, BOT projects will gain more and more importance for major projects.

3 DURABILITY Whereas cost-effectiveness is normally meant to comprise only first or construction costs, durability takes into account the life-cycle costs. Only a bridge with a minimum total of construction cost plus maintenance cost over the life of the bridge can, therefore, be considered cost-effective. The consideration of durability thus compliments the consideration of construction costs. Specifically important for cable-stayed bridges is the durability of their stay cables, in particular their resistance against corrosion and fatigue. Furthermore, cable-stayed bridges are sensitive to wind attack because of their lightness and they are also sensitive to ship collision if located in navigable waters. 21

Table 1. Characteristics of different types of stay cables. Modern locked coil rope

Parallel wire cable

Parallel strand cable

0,170 1470 150 180 31,0 >1000 >80

0,205 1670 200 499 Ø 7 32,1 250 23

0,195 1870 200 109 Ø 0,6 24,5 ≈ 200 ≈ 20

Characteristics E·10−6 fu σ biggest cables fabricated so far

[N/mm2] [N/mm2] [N/mm2] Ø [mm] pu [MN] L [m] max G [t]

Figure 12. Aerodynamic Stability of cable-stayed Bridges versus Suspension Bridges.

Figure 13. USA.

Houston Ship Channel Crossing, TX,

3.1 Stay cables The historical development of stay cables went from locked coil ropes to parallel wire cables to parallel strand cables. This development was intended to improve their durability with respect to corrosion and fatigue and to decrease their costs. In addition, locked coil ropes require large machinery which is only available in Europe whereas wire and strand cables can be assembled locally or even on site. 3.2 Wind resistance Cable-stayed bridges are inherently stiffer than suspension bridges. A comparison of the two bridge types shows that for a main span of 500 m the critical wind speed for a cable-stayed bridge is about double that of a suspension bridge (Fig 12). The Houston Ship Channel Crossing at Baytown (Fred Hartmann Bridge) is located in a hurricane prone area near the Gulf of Mexico (Fig. 4). The open cross sections for the twin beams were shown analytically to be stable during construction for a wind speed of up to 170 km/h, not enough for the expected considerably higher hurricane wind speeds. The beams were thus tied down to the tower foundations (Fig. 13) and indeed remained stable during a hurricane, which hit the site shortly before beam closure. Another striking example for the aerodynamic stability of cable-stayed bridges is the Helgeland Bridge in Norway (Fig. 14) which was designed by LAP in collaboration with Aas-Jakobsen. With a main span of 425 m the concrete beam has a depth of only 1.2 m and a width of 12 m thus rendering 22

Figure 14.

Helgeland Bridge, Norway.

Figure 15.

Helgeland Bridge, Storm.

a vertical slenderness of 1:354 and a horizontal slenderness of 1:35. (The horizontal slenderness is critical, because it prevents reattachment of the vortices from the leading edge.) The wind climate near the Polar Circle is very serious. Wind speeds up to 180 km/h with a turbulence intensity of up to 25% had to be expected and did indeed occur even during construction (Fig. 15). During severe storms just before center joint closure, the displacement of both cantilevers came to about 0.6 m, exactly as analytically predicted. In the final stage the bridge proved to be stable against flutter analytically and in tests up to a wind speed of 270 km/h. Both examples show that properly designed and analyzed cable-stayed bridges are durable against wind action, not only in the final stage but also during construction. 3.3 Resistance against ship impact Major waterways with sea-going ship traffic require large navigational clearances. Cable-stayed bridges are often the appropriate type of structure for such crossings. Special consideration must be given how to protect a bridge against collision with major ships which may exert high impact forces. The results of collision tests (Fig. 16) were used by the author to estimate collision forces as a function of ship size and speed (Fig. 17). The probability whether a pier under consideration will be reached by a ship must also to be investigated. Several types of protective measures can be used as outlined below. The safest method to protect piers from ship collision is to place them out of reach on land. The additional costs for an increased span length may be offset by savings for pier protections. Examples are the Yang Pu Bridge with a record span due to navigational requirements and the Second Panama Canal Crossing where the main span length was determined by taking into account not only the current Canal width but also future widening of the Canal to avoid ship collisions. If the water is too wide to be crossed without piers in navigable waters artificial islands may be possible. Their advantage is that they stop a ship slowly thus limiting the extent of damage to the ship’s hull. Their use is often limited if they reduce the flow cross-section too much. For the Houston Ship Channel Crossing (Fig. 4) an artificial island was built for the foundation of the one tower which had to be placed in shallow water. A similar situation exists for the Kap Shui Mun Bridge in Hong Kong (Fig. 5). If these two options are not possible it may be economic to strengthen the piers and their foundations sufficiently to withstand a collision. In this case the vertical loads from the bridge are favorably combined with an increased horizontal resistance of the foundation. Examples are the Ma Chang Bridge (Fig. 10) and the Helgeland Bridge (Fig. 14). All piers of the Rosario-Victoria Crossing in Argentina (Figs. 18 and 19) rest on pile foundations. In 30 m deep water with local scour of up to 12 m a free pile length of up to 42 m has to be taken into account. Independent defense structures, designed as sacrificial structures by exploiting their plastic capacities were the appropriate solution. 23

Figure 16.

Collision Test by Voisin.

Figure 18.

Rosario-Victoria Bridge, Ship Collision.

Figure 17. Svensson.

Figure 19.

Equivalent Collision Forces by

Rosario-Victoria Bridge, Pier Protection.

The durability of cable-stayed bridges can be safeguarded by applying one of the above counter measures against ship collision

4 CONCLUSION Since their rediscovery in the 1950s cable-stayed bridges have developed into cost-effective and durable structures, always provided the experience in design, construction and maintenance gained since then is carefully applied. The cost-effectiveness is realistically determined by the contractors in competitive bidding. Durable cable-stayed bridges require stay cables robust for corrosion and fatigue, and require as well resistance against the attack of wind and earthquake. By optimizing the cost-effectiveness and the durability of cable-stayed bridges the minimal life-cycle costs are achieved.

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Bridge Maintenance, Safety, Management, Health Monitoring and Informatics – Koh & Frangopol (eds) © 2008 Taylor & Francis Group, London, ISBN 978-0-415-46844-2

A new concept of orthotropic steel bridge deck Man-Chung Tang Chairman of the Board, T.Y. LIN International, San Francisco, USA

ABSTRACT: A new concept of orthotropic steel bridge deck is proposed to improve its durability and economy. It is suggested to hot-roll the longitudinal ribs. Thus, the ribs can be made larger and with a more effective cross section that is not possible for cold bent ribs. Together with a thicker top plate these ribs can be spaced at 800 mm apart and span 8 meters or longer. This will significantly reduce the cost of fabrication of orthotropic decks while the unit weight per square meter remains practically the same. An orthotropic deck with such a configuration will be more economical and more durable.

1 INTRODUCTION In a contemporary design of the orthotropic steel deck, the deck, besides supporting all traffic loads, it is a part of the upper flange of the girder and is the upper flange of the transverse floor beams. This saves material and results in a light weight system which is very important for long span bridges. In mid 1950s, W. Cornelius presented a simplified method for the analysis of orthotropic deck with trapezoidal ribs. Later, G. Fischer’s contribution, with consideration of the torsional stiffness of the ribs, simplified the design of close rib orthotropic deck which is more economical. However, Cornelius, with the firm MAN, patented the trapezoidal rib configuration in late 1950s. This forced other construction firms to use many other shapes for the ribs, such as rounded shape, wine glass shape, etc. as shown in Fig. 1, which were usually less efficient. Lately, almost all orthotropic decks have the closed trapezoidal, torsional stiff ribs. The trapezoidal ribs are more efficient and more economical. However, the fabrication of orthotropic steel deck is more labor intensive and requires much more stringent quality control than a concrete deck. Therefore, for economic reasons, it was not widely used after the reconstruction period except for very long span bridges where weight saving is of utmost importance. The bridge building of Japan and later in China revitalized the idea of orthotropic deck. This is especially true in China where labor is relative inexpensive, many medium to long span bridges are finding the use of orthotropic steel bridge deck attractive. Almost all recent bridges have exclusively trapezoidal ribs. For this reason, all further discussion in this paper will concentrate on orthotropic decks with closed, trapezoidal ribs.

Figure 1. Various shapes of longitudinal ribs.

25

2 COMMON PROBLEMS IN ORTHOTROPIC STEEL BRIDGE DECKS A new concept of orthotropic steel bridge is proposed in this paper is to avoid problems already found in existing orthotropic steel decks. It is therefore important to recognize what problems are there in the existing bridge decks. Since its application in the 1950s, various problems have been discovered in the orthotropic decks. In general the problems can be divided into two groups: the failure of the steel deck and the failure of the pavement. Very often, it has been a common practice that the steel deck is designed by the structural engineer while the pavement is designed by a material engineer. They usually do not communicate with each other. However, in reality, the steel deck acts compositely with the pavement as a monolithic structural system and they must be analyzed together as one unit. Improperly designed steel deck can cause the pavement to fail while an improperly designed pavement can create high stresses in the steel deck. This fact has only been properly addressed in recent years. 2.1 Failure in the orthotropic steel deck Cracking in orthotropic steel deck has been reported in many literatures. These cracks are mainly caused by stress concentrations in steel members due to local constraints. They can be generally grouped into the 4 types of cracks as shown in Fig. 2. A. Under the wheel load, the stress at and near point A can be very high. This is because the deck plate is supported on the one side by the web of the floor beam or diaphragm while there is no support on the other side, above the trough of the rib. Kolstein calculated 200 MPa (29 ksi) for this stress in a 12 mm deck plate. C. Seim measured 33 ksi (225 MPa) in the 11 mm deck plate of the Luling Bridge. The bending moment at this location under the wheel of the vehicle is rather constant while the stress increases when the deck plate gets thinner. Cracking at this point was found mainly in deck plates with a thickness 12 mm or less. For deck plates 14 mm or thicker, such cracks are rather uncommon.

Figure 2.

Common problem spots in an orthotropic steel deck.

Figure 3.

Stress concentration at discontinuity spot A.

26

One attempt to address this problem is to install a diaphragm in the trough of the rib to provide support to the deck plate. This diaphragm, or filler plate, however, is rather costly and difficult to install. Except for area where there is a compression force in the transverse direction of the deck that requires the diaphragm to transfer this force, the tendency is not to use this diaphragm in the trough. A thicker deck plate is a better solution for this problem. B. Point B is the intersection of three welds: the fillet weld (1) between the web of the rib and the deck plate, the horizontal weld (2) between the deck plate and the floorbeam web, and the weld (3) between the rib wall and the floorbeam web. For a long period of time, it has been a rather standard practice to cope the corner of the floor beam web to separate these three welds. However, to obtain a really good detail the end of both weld 2 and weld 3 must be properly rounded and ground smooth, which is usually not done due to cost of labor. Such a detail will lead to fatigue and corrosion problems. Recent practice has been not to cope the floorbeam web and let these welds intersect each other. C. When a vehicle travels on the bridge deck, the wheels advance from floorbeam to floorbeam. The longitudinal ribs deflect up and down under the wheel load depending where the wheel is located. This up and down bending of the rib creates a longitudinal movement of the rib wall at point C, which translates into an out of plane bending of the floorbeam web at this location, Fig. 4. This point C is especially vulnerable because it is also the end of a difficult weld. To reduce the stress concentration at this point, a detail as shown in Fig. 5 is usually recommended. But such a detail is very labor intensive and therefore expensive. Another option which has been used successfully is to delete the opening and use a round bottom rib and a continuous weld between the rib wall and the floorbeam web.

Figure 4.

Rotation of rib and Floorbeam Web under Wheel Load.

Figure 5.

Detail at Point C.

27

D. This point is away from the floorbeams. Because the ribs are closed, this weld can only be produced from the outside face. The prevailing requirement is to have a weld size of about 80 to 85% of the rib web thickness. Blow-out is not allowed. It makes this weld difficult to achieve. In addition, even if the weld is done properly, it is still an eccentric weld with respect to the thickness of the rib wall because the weld is on one side only. There are other problems involved with the orthotropic decks. However, the above mentioned problems are the major ones. 2.2 Problems in the pavement There are mainly two types of paving material used on orthotropic steel decks: bituminous type and polymer type. Mastic asphalt, Gussasphalt, etc. are bituminous type. Epoxy asphalt, polyurethane, and polyesters are polymer type. There have been some exceptions, such as concrete bonded to the deck with shear connectors. But these are really rare. The pavement on many orthotropic decks failed in a short period of time after the bridge is open to traffic. There are four main problems connected with the deck pavement: cracking, separation, or de-lamination from deck plate, rutting, and loss of skid resistance. Rutting and loss of skid resistance are mainly due to poor performance of the pavement material. Cracking and separation are mainly due to overstress or fatigue. Selection and composition of the pavement material will not be discussed here. The following discussion will concentrate on the problem of stresses. Cracking in the pavement is a result of high tensile stress in the pavement. Separation is due to the failure of the bonding layer between the pavement and the deck plate. Because the pavement is adhered to the deck plate, the entire system, including both the orthotropic steel deck and the pavement material must be treated as a monolithic structure in the calculation of the stresses in the pavement. Thus, to analyze the stresses in an orthotropic steel bridge deck with a pavement, the properties of the steel deck, which include the plate thickness, the rib spacing, the floorbeam spacing, the rib stiffness, etc. and the pavement characteristics, such as the pavement thickness and stiffness must be properly considered.. Fig. 6a shows the stress in the steel deck plate and the stress in the top of the pavement for various modulus ratio (n) between steel and the pavement material as presented by R. Wolchuk. When asphalt based pavement is used, the modulus of elasticity of the pavement material varies with temperature. The warmer the temperature, the softer the material is. Consequently, the modulus ratio can change from about 10 to about 500 in the usual range of temperature of the deck. It can be seen from Fig. 6a that the stress in both materials can change significantly. Therefore, for the design of either the pavement or the steel deck, temperature effect must be properly considered. C. Seim, R. Manzanarez and T. Ingham have explored this relationship extensively. Some of their results are reproduced in Fig. 6b to 6d. Fig. 6b shows the shear stress in the bonding layer between the steel deck plate and the pavement for an orthotropic steel bridge deck under a typical AASHTO wheel load. This is based on a deck with 8 mm thick, 280 mm high trapezoidal ribs spaced at 600 mm centers. It shows two groups of curves. The upper group is for n = 10, the lower group is for n = 500, which, together, represent the two rather extreme temperature conditions a regular bridge deck may experience. The four curves in each group are for a deck plate thickness of 10 mm, 12 mm, 14 mm and 16 mm. The important message from this plot is to show, similar to the one by Wolchuk in Fig. 6a, that the maximum stress depends on many variables. It is interesting to note that the maximum shear stress is lowest for a pavement thickness around 38 mm. Fig. 6c and 6d are results extracted from the analysis for the Second Yangtze River Bridge in Nanjing, China. It is a 628 m span cable-stayed bridge with a box shaped main girder. The deck plate thickness is 14 mm uniform over the entire bridge deck. It has 8 mm thick, 280 mm high trapezoidal ribs spaced at 600 mm centers. The data shows that the maximum tensile stress in the pavement at low temperature decreases rapidly with increase of pavement thickness until it reaches about 60 mm. 28

Figure 6.

Stresses in the steel deck and the pavement under AASHTO wheel load.

It is important to note that if the pavement thickness is very thin, say, less than 15 mm, both the maximum tensile stress in the pavement and the shear stress in the bonding layer can be very high. This probably explains why many of the thin pavements on orthotropic decks have failed. The problem compounds when the steel deck plate is also very thin. Kolstein and Wardenier have presented a detailed report on a bridge in Holland which has 12 mm deck plate and 8 mm thick pavement that had required extensive repair due to failures in both the steel deck and the pavement.

3 THEORETICAL ANALYSIS AND PRACTICAL EXPERIENCE Data in Fig. 6a-d show that the stress condition in an orthotropic bridge deck is very complex. Adding to this complexity is the hard to predict residue stresses in the welds and the cold bent steel ribs. Any numerical result appears to be rather approximate at best. Under such circumstances, performance record of existing bridge decks should be a more important gauge for future designs. Many of the recommendations in the Codes, AASHTO or Eurocode, have been based on past experience, with some help from laboratory tests of special details. Engineering is not science. Engineering is based on experience and aided by science as one of the tools. It is important to supplement complex numerical analysis with careful learning from successful experience. 29

4 DECK PLATE THICKNESS AND RIB WALL SPACING The current AASHTO-LRFD Code recommends that the deck plate thickness should be at least 4% of the distance between the webs of the ribs, which represents a deck plate span to thickness ratio of 25. It is the writer’s opinion that this may be still slightly too thin. The orthotropic steel bridge deck on three bridges have performed very well: The deck plate of the San Mateo Bridge over the San Francisco Bay has a span to thickness ratio of 24. It has performed well for over 35 years. The re-decking of the Golden Gate Bridge has also been performing well for over 20 years. Its deck plate has a span to thickness ratio of 23.3. The western suspension spans of the San Francisco Oakland Bay Bridge had preformed well for over 30 years. Its deck plate has a span to thickness ratio of 24. Only its skid resistance had declined to a level that might require repair or replacement after 30 years of continuous service. All these three bridges have 50 mm epoxy asphalt pavement. Therefore, this experience should only be applied to decks with a 50 mm epoxy asphalt pavement. There have also been unsuccessful examples of bridges with similar combinations. But each can be traced to defects in the design or construction. Both the fabrication of the orthotropic deck and the placement of the epoxy asphalt pavement require very stringent quality control. If this can not be guaranteed, the deck system can not be expected to perform well. Instead of the simple span to thickness ratio, C. Seim prefers to use the span to deflection ratio as a design parameter. Obviously, these two ratios are inter-related. The span to deflection ratio has the advantage that it can be recalibrated for a modified wheel load other than the AASHTO wheel load. But, the span to deflection ratio varies with the cube of span to thickness ratio; it is also directly proportional to the intensity of the wheel load. Any transformation will be simple. For example, if a span √ to thickness ratio of 24 under the current AASHTO load is considered acceptable, a 14.3% (= 3 1.5) decrease in the span to thickness ratio to 21 should be used if the wheel load is increased by 50%. However, this transformation considers only the deformation of the deck plate. When the wheel load is increased by 50%, other factors may become more prominent so that such simple extrapolation should only be used with extreme caution.

5 RECENT APPLICATIONS IN CHINA China is building many new long span bridges in the last two decades. The spans of these bridges are getting longer and many of them have orthotropic steel bridge deck. The deck system of several early steel bridges had problems, especially in the pavement. Most of these early bridges use a deck plate of 12 mm with bituminous type pavement. A 14 mm deck plate with 50 mm epoxy asphalt pavement was used for the first time in the design and construction of the Second Yangtze River Bridge in Nanjing. The span to thickness ratio of the deck plate of this bridge is 21.4 to allow for possible overloaded trucks that are probably unavoidable in China at the present time. This bridge was open to traffic in early 2001. The deck has been performing very well. Since then, most Chinese steel bridges, including the world’s longest cable-stayed bridge, the Sutong Bridge, have been designed with a 14 mm or thicker deck plate and most have used 50 mm epoxy asphalt pavement. The performance of these bridges has been very good until today.

6 COST OF ORTHOTROPIC STEEL BRIDGE DECK The cost of an orthotropic steel bridge deck consists of material cost, fabrication cost, transportation and installation cost. Material cost is usually less than about 35% of the total cost. A major cost is in fabrication, with the major expenses spent on the welds at the intersections of the floorbeam and the longitudinal ribs. And, this is the one item cost saving is possible in an orthotropic steel bridge deck. 30

Figure 7. The Proposed Hot-Rolled Rib.

7 A NEW CONCEPT A new concept is proposed to eliminate the known problems described above. It is based on the use of a hot-rolled rib with variable thickness as shown in Fig. 7. R. Wolchuk had suggested the use of hot rolled ribs to reduce the residue stresses in the ribs created by the cold bending process. However, hot rolling also offers the opportunity of optimization of the shape of the rib. The rib proposed in Fig. 7 is 380 mm deep, which is deeper than the ribs commonly used today. To optimize its effectiveness, the bottom portion of the rib is thickened to 20 mm. This thickening can be increased if needed for larger wheel loads or longer rib spans. This rib configuration is more efficient than the current trapezoidal ribs with uniform thickness. The bottom portion of the rib is rounded so a continuous weld can be produced easily from one end of the rib to other end of the rib. C. Seim has also suggested that the bottom 25% of this weld be a full penetration weld to further improve its resilience. Use of a rounded shape without the cut-out has performed well in a number of earlier bridges. This will eliminate the difficult and expensive weld at the termination points C as shown in Fig. 3. In connection with this round bottom rib, the web of the floorbeam or the diaphragm must be flexible. R. Wolchuk suggested that stiffeners or bottom flange that can restrain the out of plane bending of the web should be placed at a distance of at least twice the depth of the rib from the bottom of the ribs. To improve on the weld between the web of the rib and the deck plate, a local thickening is introduced to the top portion of the rib walls. This is to address the welding problem at point D in Fig. 3. The rib web thickness is increased to 11 mm at the top so it will be easy to produce an 8 mm to 9 mm weld from one side only without risking blow out. The taper of the upper face of the ribs can be made in the hot roll process to save an additional step in the fabrication. A 50 degree taper is suggested. However, this can be modified to suit local conditions. With a stronger rib, a thicker deck plate should be used to allow larger rib spacing. An 18 mm deck plate with 800 mm rib spacing will give a span to thickness ratio of 22.22 which is a satisfactory ratio based on experience described above. Such a longitudinal rib can easily span 8.00 m. With such a span, there will not be a need for intermediate floorbeam in most cases, which means, there will be only diaphragms that spaced at 8.00 m intervals. The advantage of a diaphragm over a floorbeam is that it can be made more flexible in the out of plane direction. This flexibility will reduce the stresses in the weld between the rib wall and the diaphragm from the out-of-pane bending of the diaphragm web caused by the rotation of the ribs at the diaphragm as the wheel proceeds from diaphragm to diaphragm on the deck. Such a deck is also more efficient in load transfer because it is closer to a plate action in carrying the wheel. When the rib span is very small, most of the wheel load is carried by the one single rib under the wheel. As the rib span is increased, the orthotropic deck acts more like a plate and more ribs are participating in carrying the wheel load. Without better performance record of other pavement materials, it is recommended a 50 mm epoxy asphalt pavement be used until testing can prove other pavement types satisfactorily. 31

8 COMPARISON Based on available data from recently completed long span bridges in China, the typical configuration of the orthotropic deck has 8 mm thick, 280 mm high trapezoidal ribs spaced at 600 mm center to center; Deck plate is 14 mm thick and the diaphragm, or floorbema is 12 mm thick spaced at 4.00 m. The box girder is usually 3.5 m deep. Take a 12 m wide and 16 m long deck panel. The conventional deck will have 20 longitudinal ribs and 4 floorbeams or diaphragms. Thus, there are 20 × 4 × 80 intersections of ribs and diaphragms. Such a panel, including the diaphragms will weigh about 2.81 kN per square meter. If the proposed new configuration is used, the same 12 m by 16 m panel will have 15 longitudinal ribs and 2 diaphragms with 15 × 2 = 30 intersections. The weight of such a panel is about 2.89 kN per square meter. The saving in welding is very significant. The number of intersections is reduced from 80 to only 30. And the number of welds between the ribs and the deck plate is reduced by 25%, while the weld between the diaphragms and the deck plate is reduced by 50%. In addition, the welds at the intersections are much easier to produce, without any grinding.

9 SUMMARY Modern orthotropic steel bridge deck has been in service for about 50 years. Its performance is generally quite satisfactory. However, there are still problems that have been causing failure in some bridges. It is therefore prudent to modify the current design to deal with these problems. With advanced computer software available today the analysis of any such bridge deck is not difficult. However, due the complexity of such a structure, computer analysis can only reproduce a part of the actual behavior of the deck. Various assumptions in the establishment of the computer model are idealized assumptions. The most important item missing is the residue stress due to welding and manufacturing. These stresses could easily be as high as the stresses due to live loads. These stresses do not have much effect on global stresses. They are usually very local in nature, mainly due to unavoidable local constraints in the structure. Adding to the unknown is the behavior of the pavement. The pavement is bonded to the steel deck and form a monolithic structure with the deck. Therefore, any analysis of the steel deck must include all proper characteristics of the pavement. Consequently, it is recommended that past performance record of existing decks be incorporated in the design, with the theoretical analysis giving a comparative value to the design. Past performance record of existing bridges with orthotropic steel deck has provided clues on what may or may not work. The problems in the steel deck and in the pavement have been summed up above. A new concept, or configuration is proposed to overcome or avoid these problems, both in the steel deck and in the pavement. For example, high stress concentration at Point A, Fig. 2, is reduced by using an 18 mm thick deck plate. The fatigue problem at Point C is eliminated. The welding problem at Point D is significantly improved. By using an 18 mm thick deck plate with a span to depth ratio of 22.22 the stress problems in the pavement should be eliminated based on experience gained from successful existing structures. The proposed cross section of the longitudinal rib is more efficient because it has a thickened bottom flange. With extended rib spacing and rib spans, or diaphragm spacing, the proposed deck configuration also saves extensively in fabrication costs. Obviously, to produce this new rib, the steel mill must establish a new production line to roll them. However, such a production line is not expensive compared to the possible savings in the fabrication and other advantages. A single medium size bridge will recoup all costs involved in such a production line.

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Bridge Maintenance, Safety, Management, Health Monitoring and Informatics – Koh & Frangopol (eds) © 2008 Taylor & Francis Group, London, ISBN 978-0-415-46844-2

Health monitoring of structures & related education and training needs of civil engineers A.A. Mufti ISIS Canada, University of Manitoba, Winnipeg, Manitoba, Canada

J.P. Newhook ISIS Canada, Dalhousie University, Halifax, Nova Scotia, Canada

1 INTRODUCTION The Intelligent Sensing for Innovative Structure (ISIS) Canada Networks of Centres of Excellence (NCE) program has been pursuing research and field implementation of structural health monitoring technology for innovative infrastructure using Fibre Reinforced Polymers (FRPs) to reinforce concrete since 1995. The authors of this paper have a collective record of over 30 field projects, which have employed some aspect of health monitoring technology. Concurrent with this research work, the authors have been part of an ISIS team developing resources and strategies for educating the engineering community about SHM. This includes creating a series of design manuals, such as the Guidelines for Structural Health Monitoring and the Civionics Specifications. The members of ISIS Canada have produced a variety of documents and guidelines to assist practicing engineers with the implementation of SHM systems. More recently, ISIS Canada has produced an educational module for usage in the undergraduate engineering curriculum. Concurrently, a graduate course SHM for civil engineering graduate students has been developed. Finally, the authors have been active in developing workshops, which introduce SHM to researchers and practicing engineers. Based on these activities, the authors have formulated an opinion on the education needs and changes required such that SHM can be successfully implemented in civil infrastructure management. The changes suggested will not only impact the adoption of SHM technology but will also lead to a better integration of civil engineering practices in general. This paper discusses three key elements of for implementation of performance engineering: Structural Design, Structural Health Monitoring and Civil Engineering Education. It is hoped that in doing so, further discussion and activity related to this objective will be stimulated. 2 CIVIL STRUCTURAL DESIGN PROCESS Traditionally, structural components were designed by the working stress method, which required that the maximum stress due to nominal dead loads and live ‘service’ loads was a fraction of the maximum stress that the component could withstand. The ratio of the failure stress to the ‘actual’ stress was and is still known as the factor of safety. As long as the factor of safety was a sufficiently large number, say 2 or 3, the design was deemed to be safe. While the working stress design has served the engineering community well for a long time, it has led to structures with non-uniform margins of safety. Works of researchers in the late 1960s and early 1970s laid the foundations for modern structural design codes, which are based on the concept of structural reliability. In Canada and some parts of Europe, the probabilistic-based design method is referred to as the limit states design method. In the USA, the same method is referred to the load and resistance factor design (LRFD) method. It is important to note that the working stress method, which is still practiced in many parts of the USA as well as in many other countries, was used to design a very large part of the current 33

Figure 1.

Reduction in value of safety index with time.

stock of infrastructure in practically every country. The earlier working stress design methods requiring manual calculations and based on simplifying assumptions usually led to structures with large reserves of strength. By careful use of SHM, these untapped reserves of strengths in civil structures can be utilized, thus affecting economies in the design, building and evaluation of civil structures. The use of SHM is also expected to encourage innovative structures. The level of safety of a structural component is determined by the probability of its strength exceeding the maximum load effect it would receive during its lifetime. Safety margins in a structural component are measured by the probabilistic-based safety index, β. A detailed explanation of the determination of safety index is given in the paper through reference to live load distribution in a girder bridge. The resistance of a structure ®, such as a bridge, can decrease with time due to environmental and other time-dependent effects including material deterioration and fatigue. Similarly, the live loads (S) that a bridge is called upon to carry can also increase with time, which has been experienced in Canada with the changes in vehicle weight regulations demanded by the economics of freight hauling by highway trucks. As illustrated in Figure 1, the net result of the decrease of resistance and increase of loads over time is the increase of the overlapping areas of two curves. Hence, it can be seen that the notional safety indices of the components of a bridge can decrease with time. Should such a reduction in the safety index always give us a cause for concern? Fortunately, a bridge can continue to be used even if its safety index is smaller than 3.5, but only if there is reliable knowledge about the structure. Bakht and Jaeger have shown that each time a bridge was tested surprising results were observed. The actual behaviour of bridges was usually found to be different than that of the mathematical model used in the original design. In most cases, the actual strength of bridges was considerably higher than the theoretical strength. 3 STRUCTURAL HEALTH MONITORING An interesting question that should be asked is, “Can structural health monitoring in the field be useful in managing risk?” The answer would be a resounding, “yes.” The term ‘civionics’was coined recently to be parallel to ‘avionics,’ which is defined in American English language dictionaries to denote the application of electronics to aviation and astronautics. The term ‘civionics’ refers to the application of electronics to civil structures to determine the state of their health. The use of sensors to monitor the response of a structure or its model to applied loads is not new, nor is 34

bridge evaluation by field testing, which includes both diagnostic and proof testing. What is new, however, is the use of SHM through civionics. In the past, civil engineers have gained knowledge about the integrity of civil structures largely by means of manual inspections, and rarely by nondestructive evaluation (NDE) and interpretation of data using conventional technologies. The structural engineering profession has relied heavily on the evaluation parameters given in codes of practice that lead to conservative and often costly conclusions about the strength of existing structures. In order to remain competitive in today’s global economic environment, the owners of civil structures need to minimize the user costs involved with the unnecessary closing of the structures and service disruption caused by outdated and time-consuming inspections following extreme events, such as strong-motion earthquakes, hurricanes, flash floods, or other extreme events. In the evaluation of any structural system, it is important to be able to assess specific performance issues related to serviceability, reliability and durability. To effectively quantify the system’s performance requires a means to monitor and evaluate the integrity of these large civil structures with minimal interruption of service. The SHM data, besides allowing owners to better allocate their resources towards repair, replacement or rehabilitation of the structures, will also be useful in future projects in estimating the life cycle costs of the structural system compared to the initial cost. An efficient SHM system should be autonomous and capable of continuous monitoring, inspection and damage detection. The direct benefits from SHM systems are very great and include: • • • •

monitoring and evaluating structures in real-time under service conditions; reducing downtime; improving safety and reliability; and reducing maintenance costs.

With reduced downtime and improved reliability, in-service structures can be used more productively with less cost. The CHBDC (2000) contains clauses for the strength evaluation of existing bridges; the clauses are based on the concept of a target reliability index that can change with (a) system behaviour, (b) component behaviour, and (c) the level of inspection. The system behaviour relates to the effect of the failure of a component to the failure of the whole structure; the component behaviour corresponds to the ductility of its failure; and the inspection level refers to the degree of confidence in the inspection process in determining the actual condition of the bridge and its components. In the paper, the effect of the three factors on the target reliability index is explained with the help of examples. The examples illustrate that depending upon the system and element behaviour and confidence on inspection, there can be a significant difference between two useable live load capacities for the same structure. If the condition of a component of a structure were determined with the help of sensors in an SHM system, the degree of confidence in the determination would be greater than in any visual inspection, with the consequence that the evaluator of the component would be able to utilize a larger portion of its live load capacity. The concept of the target reliability index changing with the inspection level does not exist in design of new structures. Yet, it can be appreciated that if the designer of a structure were confident that the condition of the structure and the load that it receives would be determined continually and accurately by an SHM system, he/she can afford to be less conservative, thus reducing the capital cost of the structure. Drawing upon the comparison between a fully instrumented aerospace structure and a civil structure without any sensor to report on its health, it can be stated confidently that the designers of civil structures are risk-averse to an extent because of the absence of information about the field performance of these structures. 4 CIVIL ENGINEERING EDUCATION Both industry and university participants in the ISIS Canada network recognized that the production of leading edge research results would not find widespread usage unless the innovations and ideas 35

were integrated into the engineering curriculum. ISIS Canada therefore has taken a unique step for a research organization; it has adopted education as a primary element of its mandate. To facilitate its education mandate, ISIS Canada has developed a series of Educational Modules on both FRPs and SHM technologies for use in undergraduate engineering curricula. Teaching resources, consisting of lecture notes, presentations, worked examples, case studies, and sample assignments and laboratories, have been developed. Recently, targeted educational materials have also been developed for use within engineering technology programs at the technical college level for the training of engineering technicians and technologists. Concurrent with the development of student-oriented education modules, ISIS has been developing practice-oriented manuals for use by professional engineers. The manuals were prepared for two reasons. The first is to provide practicing engineers with detailed guidelines regarding the use of SHM technology and new materials in the design and construction of civil engineering structures. The second is to provide a practical set documents completed with guidelines and background reference to supplement developing national Codes and hence facilitate and accelerate adoption of these new ideas in practice. While this approach has met with success in its objective of increasing awareness, the authors are proposing that a more fundamental change in curriculum is required. This change is not simply the production of course material or the introduction of a new course. A fundamental change in the integration of the various aspects of civil engineering is required throughout the curriculum in general. The paper discusses the authors’ thoughts on developing an integrated approach to infrastructure engineering. The traditional education approach and the proposed performanceoriented engineering approach are compared. With the aid of a case study the performance-oriented engineering approach is illustrated in detail. Finally, specific examples of education curriculum changes are provided. 4.1 Traditional education approach The two cornerstones of the traditional engineering education approach are engineering analysis and engineering design. Engineering analysis includes topics such as mechanics, determinate and indeterminate structures, linear and non-linear analysis and numerical modeling. Engineering design includes such topics as material properties and behaviour, safety and codes, sectional resistance, and selection of component geometry. A startling realty of many curriculums is that these two cornerstones are generally taught in isolation of each other. Design education still includes many simplifying assumptions in behaviour ignoring many secondary effects or including them by approximation or simply coefficients. While the resistance of a structural component in ultimate limit state may be highly non-linear, the determination of load effects is often based on approximate linear analysis and often ignores a detailed consideration of load paths. While some effects, such as cracking of concrete, are stressed in design detailing considerations they are ignored or simplified in analysis. A third component of structural engineering education is construction, including project management, which often receives very little attention in undergraduate engineering education. Even less frequently addressed are issues of service life maintenance and management of structures. Figure 2 illustrates these three subject areas with very little linkage (emphasized by the use of dashed connecting lines). The process is generally one-directional with very little feedback. 4.2 Proposed education model Currently structural health monitoring is normally discussed in the literature as a technology in its own right. Its separation from main stream infrastructure engineering is reinforced by the majority

Figure 2.

Representation of traditional education methodology and linkages.

36

of forums for discussion and for publishing literature being specialty conferences and journals. There is a real risk therefore that, if SHM was introduced into the current curriculum, it would simply be another box in Figure 2 with less or even no linkage to the other elements. If this were to unfold then SHM would remain an interesting but little-used research idea. The authors propose that for SHM to achieve wide-spread usage a fundamental change in our education approach must occur. Indeed, the change is not simply about redesigning education curriculum or philosophy but about changing the way future engineers will practice engineering as it relates to civil infrastructure. Even without SHM, it can be readily acknowledged that the model shown in Figure 2 is inappropriate. Firstly, a management activity box should be added to reflect the importance of the life-cycle engineering of infrastructure (i.e. the majority of money and effort often does not end with construction but comes throughout the remaining life of the structure). Secondly, these activities need to be integrated with strong linkages and feedback between all components. The education system needs to teach and reinforce this integrated infrastructure engineering approach at all levels of its curriculum. This is not a new concept and many progressive educators have also extolled the need for such linkages. However, it is not enough to simply state this need, particularly if the practice of engineering remains unchanged. What is required is a focal point for this integration. While SHM may seem to be a likely candidate for the focal point, it is in reality another tool or component for the infrastructure engineer. The authors propose that the proper focal point is performance. Performance in this sense needs to be considered in its broadest possible context. It includes qualitative or quantitative measures to assess the following issues: • • • • • • • •

Determine actual behaviour and compare to assumptions used in analysis. Determine actual loading and compare to design loading. Evaluate durability of structure to environmental, operational and load conditions. Assess secondary design issues such as temperature effects, joints, movements, vibrations. Identify deterioration or damage of the structure and its components. Evaluate safety and reliability of structure at any stage of its service life. Evaluate remaining service life. Assess the impact of maintenance or rehabilitation on future performance.

Whereas design and analysis are very abstract and rely on idealizations, performance is very structure specific and relies on the actual field data and assessments. SHM then becomes a vital component to obtain the field information necessary to make proper performance assessment. The model is illustrated in Figure 3. It may be argued that current infrastructure practices do have a focus on performance. This may be true for infrastructure managers but it is not fully integrated in the other stages of design. Design is often a task that ends with the production tender documents. Very few design engineers are involved in field inspections and assessment. The experience from previous poor performance is generally communicated to the designer via generic code criteria and standards. For specific structures, once the design is complete, the designer normally has no responsibility for its future performance. In many cases, construction activities are also not linked with performance. Individuals involved in construction supervision and quality control often do not see first-hand the impact of these choices during the service life of the structure. This is not merely an issue of practice but a philosophy that is reinforced by the education curriculum. Analysis is viewed as the most sophisticated of tasks yet is taught in isolation from measuring actual structural response. Design is the next sophisticated task but often relies on rigid code rules rather than reinforcing by observation of failures. The education in construction is normally more focused on scheduling and production rather performance. Field inspection and evaluation is often not even taught in engineering curricula but left to technical schools to train inspectors. 37

Figure 3.

Proposed education model and linkages.

The student engineer must be taught that the prime objective of infrastructure engineering is performance and that the individual tasks shown in Figure 3 are only successful if the performance is successful. The message cannot be fully taught in the classroom and therefore must be reinforced by laboratory and field work. The paper contains a detailed discussion of a long-term field project that the authors have been involved in for over 12 years which illustrates the integrated approach necessary to assess performance. The project used both SHM data and laboratory work to establish that fatigue cracking is the key performance characteristic of an innovative concrete bridge deck system. The performance was assessed on component and superstructure level and compared against theoretical analysis and design assumptions. Experimental work was necessary to supplement an understanding of the SHM data being collected. A rigorous theoretical approach is now being developed to establish a better performance diagram for fatigue monitoring. Based on the performance evaluation of this and other similar structures, changes in design and construction details were implemented in future projects and eventually into code documents. The SHM system was constantly evolving as the knowledge and the understanding of the performance issues and the key response parameters evolve. Throughout all this activity, understanding and improvement of performance was the prime objective and was greatly aided by SHM activities. The paper also discusses the impact of design changes on performance. In response to observed issues in the field, design details and criteria can be changed to address that specific concern. A performance-oriented engineering approach would force us to consider the impact of these design changes not just on the specific issue of concern but on all performance issue for the structure. These issues are discussed with specific reference to the field case study. In one scenario it is shown that changing the design to improve one aspect of performance (i.e. cracking) may actually reduce another (i.e. fatigue life). In the second scenario, the danger of combining new technologies with full investigation is highlighted. It is shown that two distinct technologies that have been designed to address the same general performance issue of corrosion of steel-reinforced bridge decks may actual create new performance issues if combined. Both scenarios are meant to illustrate the importance of developing a performance-oriented rather than design-oriented engineering approach to technology and infrastructure improvement. 4.3 Changes to undergraduate curriculum The paper also presents some specific suggestions for changes to the undergraduate curriculum will be discussed. Perhaps the most important need is to re-emphasize the importance of physical observation in developing an understanding of structural engineering. With the maturation of numerical methods such as finite element modeling and the easy access to user-friendly commercial packages, many educators have focused on theoretical approaches to analysis. In addition, electronic representative of components and behaviour made convenient by graphics software has replaced physical models. Students have lost the inherent ‘feel’for the structure; but, more importantly do not fully understand 38

that the numerical modeling, albeit sophisticated, is still just a theoretical representation of actual behaviour based on simplified assumptions. It is the actual response they need to understand not simply the theory behind the models. The linkage with SHM activities is very strong on this point. Recorded field data contains all the complexities of response, including issues that are normally classified as secondary in design or ignored in analysis. Interpretation of field data therefore requires a higher level of understanding than is often found in design. In fact, if an engineer is attempting to design an SHM system with compensated gauges to eliminate unwanted effects such as temperature in the recorded response, then the level of understanding needs to be even higher. The authors propose therefore that performance-oriented education needs to include significant laboratory work and, where possible, field work on instrumented structures. To illustrate some possible specific activities as well as maintaining a connection with the case study of section 4, this lab work should include such activities such as measuring response a strain profile throughout the girder depth and then using that information to determine neutral axis location and composite behaviour. Ideally the experiment should be designed such that gauge readings include the effects of temperature and the girder response includes both torsion and flexural components. The latter may only be possible if access to field structures is provided. Challenging the students then designing a strain monitoring system to isolate or compensate for each phenomenon should be part of the assignment. In addition, students should be given an assignment to calculate the magnitude and configuration of the applied load from the recorded values. All these activities not only develop tools necessary for interpreting SHM data, but also reinforce and supplement the traditional education material in mechanics, analysis and design courses. Laboratory projects focusing on the effects of fatigue and the concept of cumulative damage should also be developed. Students should measure such parameters such as crack width, deflection and strain of a component and develop a curve of cumulative damage versus number of load cycles. In the time span of a regular undergraduate course, the stress range may have to be high to develop significant damage in a low number of cycles. Project groups can be formed where each group performs a different number of fatigue load cycles and then tests the component to failure. This will enable the students to make an assessment of whether the damage they observed (change in condition) affected the structural capacity (change in safety). Considering the two issues together rather than separate provides an understanding of performance. If possible the experiments should be designed in such a way that the initial defection or crack width meets prescribed design limits but after some level of cumulative damage, the prescribed limits are exceeded. This will reinforce serviceability performance as well as enable the students to understand that it is not just the initial design that must meet specific criteria but that a structure must continue to perform throughout its service life. The authors do not believe that structural engineering students need extensive training in fundamental sensory and sensor system technology. In their education, they should be exposed to many sensor types but their undergraduate level understanding should be limited to basic physics principles, such as change in resistance or a change in wave length can be used to determine strain. The focus should remain on data interpretation and performance assessment. Within the limit of this paper, only a few example activities could be provided. But they do illustrate the nature of the activities required and the need for physical not virtual experience. The proposed changes are also consistent with recent education initiatives in project-based learning and in teaching outside the classroom environment.

5 CONCLUSION The authors propose that a change in education to a performance-oriented engineering curriculum is necessary. An emphasis on learning in the physical environment of the lab and the field is preferred over the virtual environment of the classroom. In both instances, effective use of SHM will be required to properly understand and assess performance. 39

Bridge Maintenance, Safety, Management, Health Monitoring and Informatics – Koh & Frangopol (eds) © 2008 Taylor & Francis Group, London, ISBN 978-0-415-46844-2

Practical implementation of probability based assessment methods for bridges I. Enevoldsen Ramboll, Virum, Denmark

ABSTRACT: This paper presents the practical implementation of probability based assessment methods to road and rail bridge structures. For the structures analysed, modelling of the critical limit states is described as are the statistical techniques employed in modelling the loads and resistances. The overall aim of the analysis was to achieve higher load ratings for the structures considered than those which resulted from traditional deterministic analysis. Ultimately the benefits to bridge owners/managers of performing probabilistic assessments are apparent from the results, which consistently provided (a) higher load ratings for the bridges considered and (b) considerable financial savings (both direct and indirect) through the avoidance of unnecessary repair/replacement of serviceable highway structures. Examples presented in the paper demonstrate direct monetary savings in excess of $30 ml (USD).

1 INTRODUCTION A common problem among bridge owners/managers is the need to reduce spending whilst attempting to operate and maintain an increasingly ageing bridge stock which is subject to a loading intensity for which, in many cases, it was not designed. The problem is compounded by the ever increasing trend in motorway traffic frequency which was seen to double in the decade 1992 – 2002 and by the debate regarding the need to increase legal weight limits for trucks and trains and/or to provide special routes/networks which they can use. By way of example, in Denmark, the Danish Roads Directorate (DRD) have established a so called Blue Road Network which comprises roads with no bridges having a class less than 100. A classification of 100 implies that the structures along the network are capable of simultaneously carrying a 100 tonne and a 50 tonne vehicle in normal passage (i.e. no restrictions on vehicle positions on structure, full dynamic factor applied to vehicles whose silhouettes are specified). As the blue road network includes all motorways and many other major roads it ties together transport routes throughout all of Denmark. The police and road/bridge administrators use a map of the blue road network when preparing special weight permits while haulage contractors use it when planning transports and selecting routes. The wider provision of such routes internationally would clearly simplify the process of facilitating heavier trucks and trains to transport freight. This is a pressing issue which must clearly be addressed when considered within the context the European Unions (EU) own projections for a doubling in the volume of freight transported by road in the period 2000 – 2030. The problem with such projections of growth is how it will be accommodated on an already congested network. One partial solution could lie in permitting larger transports (i.e. longer and heavier trucks and trains) to operate on road/rail networks. However the problem with such a solution lies in the verification that structures along such routes have adequate capacity for these super transports. Given that in the vast majority of cases these structures were deterministically designed for loads far less than those which we would call upon them to carry in the future. Then it is clear that deterministic assessments would prescribe that extensive rehabilitation/strengthening projects would be needed for any proposed increase in allowable loads. However, the economic costs associated with such a continent 41

wide process would undoubtedly prove prohibitive and as such a departure from deterministic thinking/methods is required if the proposed partial solution is to be realized or even considered. Bearing these factors in mind the past decade has seen increased interest by bridge owners and managers in the use of probabilistic methods for the assessment of their bridges specifically within the context of documentation of higher load carrying capacities such that unnecessary repairs/rehabilitations can be avoided. Employed once a deterministic assessment of a structure has rendered a repair/rehabilitate/replace now scenario, the methods have been demonstrated to provide significant cost savings where the required safety of the structure at higher load levels can be demonstrated by probabilistic methods. This paper presents a number of case studies where probabilistic methods have been employed to validate the safety of structures for higher load carrying capacities than documented by deterministic assessment. The direct result of which has been the avoidance of unnecessary repair/rehabilitation/replacement of a serviceable structure and their inclusion on the network for heavy transports. The majority of cases are selected from Danish experience, as it is the Danish Roads Directorate (DRD), which leads the way amongst European agencies in the use of probabilistic methods as an assessment and management tool. This fact is evidenced by their publication in 2003 of a formal guideline for probability-based assessment of the load carrying capacity of highway structures (DRD 2003). However, the methods are receiving increased acceptance internationally and in this regard the main paper also presents examples of the application of the methodology to a sample of bridges in Sweden.

2 PROBABILITY BASED ASSESSMENT The basis of probability-based assessment of existing bridges lies in evaluation of the structures individualised safety. In this regard, the basic principles of the approach are no different to those employed in the derivation of design codes. The advantage however, lies in the fact that in adopting a structure specific approach the methods does not to the same degree suffer from the inherent conservatism of design codes which must necessarily generalise in order to be widely applicable. The methodology proposed for practical application of probability-based methods to safety assessment of existing bridges in Denmark, is taken from the guideline for probability-based assessment of the load carrying capacity of highway bridges which has been produced by the Danish Roads Directorate (DRD 2003) with Ramboll as consultants.

3 EXAMPLES OF PROBABILISTIC ASSESSMENT OF EXISTING BRIDGES In the following, examples of the application of probability based assessment to existing bridges are presented. The cases presented represent both road and rail bridges. The examples are significant in that they show that (a) in many cases probability based methods can be employed to demonstrate higher structure load carrying capacities than deterministic methods thereby avoiding unnecessary repair/replacement of serviceable structures and that (b) in cases where sufficient capacity cannot be demonstrated that probability based methods can be employed as an efficient management tool to optimise rehabilitation. 3.1 Vilsund Bridge, Denmark The Vilsund Bridge, illustrated in Figure 1, is a 381 m long steel bridge from 1939 consisting of 5 ordinary 67.8 m spans and a 34 m bascule span. The two lane road bridge has a width of 8.6 m with a concrete slab deck supported by a steel girder system with cross girders for every 5.58 m. The Danish Road Directorate decided that it would be desirable to allow trucks with a total weight of 100 metric tons to pass the Vilsund Bridge instead of a maximum truck weight of 50 metric tons. (Trucks with a weight above 50 metric tons must take a 150 km long detour if the Vilsund Bridge 42

Figure 1. Vilsund Bridge, Denmark. 5 ordinary spans and 1 bascule span.

cannot be passed). Analyses of the bridge were performed according to the general approach for classification of existing bridges in Denmark with Class 50 as a result, which corresponds to a situation where two Class 50 trucks with an approximate weight of 50 metric tons, are passing each other on the bridge in the most critical situation for the considered structural element. The results of the deterministic analyses showed that the critical structural members are the main cross girders supporting the concrete deck and some of the steel truss members in the ordinary spans. A rough estimate of strengthening cost of the Vilsund Bridge to Class 100 was found to be $4 million. Instead of performing the strengthening project, it was suggested to perform a bridge specific reliability analysis of the critical elements in order to reduce or eliminate the costs of the strengthening project. The reliability evaluations were split into probabilistic-based evaluation of (a) the main cross girders and (b) of the critical steel truss members in the main structure. The results of the probabilistic assessment showed that the structure could be classified in Class 100, and as such the proposed strengthening project was avoided without compromising on the safety of the bridge deck. 3.2 Storstroem Bridge, Denmark The 3.2 km long Storstroem Bridge connects the Danish Island of Zealand (on which Copenhagen is located) with the southern Danish islands of Falster and Lolland. The contract for the building of the bridge was given to the British company Dormann, Long & Co., who also fabricated the main steel structure. The contract was awarded to a British company as a political move to offset the significant trade deficit which had developed between the UK and Denmark at this time due to Danish pork exports. Until 1985 when the Faroe Bridge opened, Storstroem Bridge was the only fixed connection between Zealand and the southern Danish Islands. The Faroe Bridge carries only cars. Today the Storstroem Bridge carries only local traffic with an average annual daily traffic (AADT) of about 8000 vehicles. The main deck slab of the 3.2 km long Storstroem Bridge has suffered serious deterioration to both the concrete and reinforcement. Replacement of the bridge would be extremely costly especially when considered in connection with the possibility of the construction of the Femern Bridge at some point in the future. The bridge only carries local traffic, bicycles and pedestrians and trains. If the Femern Bridge is constructed, then the Storstroem Bridge may need to be extended from one to two train tracks. Thus, the DRD would like to postpone any decision on a strategy for the Storstroem Bridge until a decision about the Femern crossing is made. However, at the same 43

Figure 2.

Storstroem bridge. Table 1. Results of deterministic and probabilistic assessment; O’Connor et al (2004). Load Combination

Self Weight + KL10 Live Load

Deterministic plastic load carrying capacity Probabilistic Assessment: No deterioration Probabilistic Assessment: Stochastic modelling of deterioration according to inspections results

61% pf = 2.94 x 10−13 β = 7.20 pf = 6.92 x 10−7 β = 4.83

time the DRD must ensure that the structure has sufficient structural safety for both vehicles and pedestrians at all times. A deterministic assessment of the deck slab using plastic response models produced a maximum load factor of 0.61 for combined dead and live load, Table 1. This implied that the slab was incapable of sustaining the applied load. The recommendation would therefore involve costly rehabilitation of the structure. The result of a probabilistic assessment was a reliability index of 7.2 (greater than the required 4.75 (DRD 2003)) without taking deterioration into account thereby verifying that the applied load could be sustained. To obtain an accurate measure of the current deterioration a number of inspections were made in 2002 at critical locations, previously determined as the area close to the transverse joints. From the inspections a conservative deterioration model was made. Analyses using this model gave a reliability index of 4.8 in 2002. The results of the assessment of the structure performed by Ramboll are listed in Table 1, where β represents the safety index. Probabilistic assessment using a prediction of the future deterioration of the road slab identified that the safety of the road slab could not be maintained for heavy trucks unless the transverse joints with the most severe deterioration were continuously repaired. If this was done the remaining lifetime of the road slab was estimated to be at least 10 years. The repair of the transverse joints is continuing so that the most deteriorated joints are being repaired. The cost of these local repairs are insignificant to any major repair or indeed compared to replacement of the road slab. 3.3 Bergeforsen railway bridge, sweden Bergeforsen railway bridge is a single track bridge which was constructed in 1923. The bridge is situated on Swedish rail’s Sundsvall-Härnösand line, approximately 350 km north of Stockholm. The superstructure of the bridge is composed of riveted trusses with spans of 42 + 84 + 42 = 168 m as illustrated in Figure 3. Simply supported side approach spans of 22.5 m and 11.6 m give a total bridge length of 202.1 m. The superstructure of 42 + 84 + 42 m is supported at 4 longitudinal locations, 1-fixed + 3-roller, which essentially results in the bridge working as a continuous beam over 3 spans. Deterministic assessment of the bridge was performed according to the Swedish Assessment code, BVH 583.11, using the train load model BV-3 (i.e. a trainload model with 25 tonne axles and 44

Figure 3.

Bergeforsen railway bridge.

8 tonne/m line load). Structural analysis was performed in two phases using a 3d finite element (FE) beam model of the bridge constructed using the FE software LUSAS. The first phase of the analysis focused on the Serviceability (SLS) and Ultimate Limit States (ULS) while the second phase considered the Fatigue Limit State (FLS) using Rain Flow counting employing actual train silhouettes. The results of the deterministic assessment demonstrated that while the structure had sufficient capacity with respect to the Serviceability and Fatigue Limit States, that at a number of locations the structure failed to demonstrate the necessary Ultimate Limit State (ULS) capacity and as such some form of strengthening was required. As this conclusion would prove extremely costly, rather than immediately accepting the consequences of a traditional decision making process, in which this failure in a deterministic assessment would lead to a requirement for strengthening/ rehabilitation of the bridge, Banverket’s management strategy focused on an alternative decision process which would permit a probabilistic assessment of the structure to be performed to see if the necessary capacity could be demonstrated. Where sufficient capacity could not be demonstrated by the probabilistic approach it was intended that a probability based decision process would be implemented which would provide a rigorous/robust decision methodology and consequently provide information on the optimal maintenance strategy. The legal justification for this process was obtained from BVH 583.11 where it is stated that Banverket permits probability-based assessments. In the majority of cases analyzed the probabilistic assessments were able to demonstrate sufficient capacity, i.e. β > 4.8 for the elements and joints considered. However, in the case of 2 joints, probabilistic assessment could not succeed in avoiding some level of strengthening. Figure 4 illustrates one of the joints, circled, for which the calculated β = 4.51, which, as it was < 4.8 could not be deemed to satisfy the minimum safety requirements. Two sample proposals for strengthening the joint were considered, both of which involved removal of certain rivet groups from the joint and their replacement with high strength bolts. Option A, labelled in Figure 4(c) considered replacement of the central rivets, encircled in Figure 4(c) and labelled A, with 27 mm diameter bolts, while option B, encircled in Figure 4(c) and labelled B, considered replacement of the bottom two rows of rivets with bolts. In both cases the probabilistic model which was established for safety analysis of the joint was used to recompute the revised structural safety on the basis of the proposed joint strengthening methodology. The results of these re-assessments were, Option A β = 6.05 > 4.8 and Option B β = 7.80 > 4.8. The significance of these results lies in the way in which they demonstrate the ability of the probabilistic model to assess the relative efficiency of proposed repair methods and as such to be used not only in safety assessment of structures to demonstrate increased load carrying capacity, relative 45

Figure 4.

(a), (b) Connection for which β < 4.8, (b) Possible alternative repair scenarios.

Table 2. Results of deterministic and probabilistic assessment; O’Connor et al (2004). Phase 1 Deterministic Phase 2 Advanced Deterministic Phase 3 Probability Based Assessment ($USD) Assessment ($USD) Assessment ($USD) Consultant Fee Contractor Fee Project Management Total Cost

$0.1 ml $3.2 ml $0.3 ml $3.6 ml

$0.2 ml $1.1 ml $0.2 ml $1.5 ml

$0.28 ml $0.47 ml $0.1 ml $0.85 ml

to deterministic assessment, but also to be used as a tool in optimising maintenance/rehabilitation planning for structures which are determined to require some level of repair/rehabilitation to satisfy specified minimum safety criteria. The results of the assessment represented a considerable economic saving for the bridge owner through the avoidance of unnecessary repairs and the optimisation of repairs where they were indeed required. The extent of this saving (in direct costs only) is evidenced in Table 2. Here associated costs for (a) Consultants Fees, (b) Contractors Work and (c) Project Management are presented for the results from 3 phases of the project (1) DeterministicAssessment, (2)Advanced Deterministic Assessment incorporating updated structure models and rain flow analysis for fatigue 46

Table 3. Examples of DRD savings from probability based assessments. Bridge

Result of Deterministic Analysis

Probability-based assessment

Cost Saving $(USD)

Vilsund Skovdiget Storstroem Klovtofte 407-0028 30-0124 Norreso Rødbyhavn Åkalve Bro Nystedvej Bro Avdebo Bro

Max W = 40 t Lifetime ∼ 0 years Lifetime ∼ 0 years Max W = 50 t Max W = 60 t Max W = 45 t Max W = 50 t Max W = 70 t Max W = 80 t Max W = 80 t Max W = 50 t

Max W = 100 t Lifetime > 15 years Lifetime > 10 years Max W = 100 t Max W = 150 t Max W = 100 t Max W = 100 t Max W = 100 t Max W = 100 t Max W = 100 t Max W = 100 t TOTAL

4,000,000 13,200,000 2,500,000 2,200,000 175,000 175,000 600,000 600,000 1,750,000 2,200,000 3,300,000 >30,000,000

assessment and (3) Probability based assessment performed at critical locations as determined in Phase (2). It is noted that the Consultants Fee in Phase (2) includes that of Phase (1) and that that in Phase (3) includes those of Phases (1 + 2). It is also significant to point out that these are direct costs only and do not consider indirect costs associated with user- & freight delays which would have been associated with any major rehabilitation work to be performed on the structure. 3.4 Additional Cases from Denmark The Danish Roads Directorate pursues probability based assessment as a matter of course for all structures which have failed a deterministic assessment. As evidenced the results of this policy have provided significant savings in both the direct and indirect costs associated with bridge rehabilitation or replacement. In addition to the cases presented, Table 3 lists the direct monetary benefits, in excess of $30,000,000 (USD) accrued in some recent cases where probability based assessments have been employed. Photographs of some of the structures listed in Table 3 are presented in Figure 5. In Table 3 the documented load carrying capacities resulting from the deterministic and probabilistic methods are also presented. In this regard, and with reference to Figure 5(a) deterministic assessment yielded a capacity W = 50 t, which inferred that the bridge was capable of simultaneously carrying 2 No. standard 50 t trucks side by side in normal passage conditions (i.e. no restrictions on vehicle positions on structure, full dynamic factor applied to vehicles) whereas probabilistic assessment W = 100 t documented that the structure could safely carry a 100 t and a 50 t truck side by side in normal passage conditions. The wide applicability of the probabilistic methodology is apparent from Figure 5, where a wide range of structural forms/geometries to which the method has been successfully applied is presented. 4 CONCLUSIONS This paper presents the practical implementation of probability based methods to the assessment of bridge structures with the aim of demonstrating higher load carrying capacities. In all cases presented deterministic assessments concluded that strengthening or rehabilitation of the structures was required if the bridges were to be kept in service. However, more thorough probabilistic analysis of the structures at their critical limit states demonstrated, in most cases, that they did indeed have the load carrying capacity to remain in service without strengthening works. In the case where probabilistic assessment could not document adequate capacity it was demonstrated how the methodology could be employed to optimise rehabilitation of the structure. In all cases the results represented significant savings for the bridge owners both in terms of the direct replacement 47

Figure 5.

Practical Examples of Probability Based Assessment of DRD Structures.

cost and with respect to indirect costs, i.e. user delay costs, which would have been incurred during rehabilitation of the structures. It is important to stress that at no stage was the safety of the structures compromised, rather a more realistic and bridge specific safety assessment was performed which was shown to be free from the generalisations of deterministic codes. REFERENCES BVH 583.11, (2000), Bärighetsberäkning av järnvägsbroar, Handbok BVH 583.11 Banverket, 2000 (In Swedish “Assessment of railway bridges”) Danish Roads Directorate, DRD, (2003). Guideline for reliability based classification of the load carrying capacity of existing bridges. Available from Danish Roads Directorate’s website www.vd.dk

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Bridge Maintenance, Safety, Management, Health Monitoring and Informatics – Koh & Frangopol (eds) © 2008 Taylor & Francis Group, London, ISBN 978-0-415-46844-2

Bridge monitoring in Japan: The needs and strategies Y. Fujino & D.M. Siringoringo Department of Civil Engineering, The University of Tokyo, Tokyo, Japan

1 INTRODUCTION This paper gives an overview of development of bridge monitoring in Japan. The paper consists of three parts: 1) backgrounds of bridge monitoring development in Japan, 2) concept of monitoring, and 3) strategies implemented in bridge monitoring.

2 BACKGROUNDS OF BRIDGE MONITORING IN JAPAN The need for monitoring in Japan was originally influenced by its geographical conditions. Due to the facts that Japan is prone to natural disaster and has severe environment for deterioration, monitoring of environment and loading conditions with regard to natural hazard have been realized for several decades. Natural disasters such as earthquakes and typhoon are some of the major concerns for civil engineering construction and maintenance. In its report (Japan MLIT 2005), the Japan Ministry of Land, Infrastructure and Transport (MLIT) has listed natural disaster as top factors that are threatening the sustainability of infrastructure. From 1970 to 2004, the total infrastructure loss due to natural disaster is approximately US$ 165 billion, or 15% of the world’s total infrastructure losses caused by natural disasters. In 1995, Kobe earthquake alone killed more than 6000 people and heavily damaged major infrastructure systems. The earthquake caused extensive damage to highway bridges in the national highway and local expressways network. To anticipate the similar scale of earthquake in the future, bridge seismic design code was later revised. Constructions of new bridges are subjected to the new code, while the existing bridges are undergoing seismic assessment and retrofit program to meet the demand required in the new code. In the context of a bridge retrofit and seismic assessment program, structural health monitoring (SHM) plays an important role. Many bridges in Japan especially the long-span ones are instrumented with permanent sensors. This instrumentation provides seismic or/and ambient responses that are essential to obtain insight into the real behavior of bridges during different loading conditions. Another geographical aspect that influences Japan infrastructure, and bridges in particular, is the country’s topography. As an archipelago country, Japan consists of mountainous islands with population mainly concentrated near the seashore. Therefore, transportation infrastructures including many bridges are built near the coast line, and some are crossing the channel, such as the world longest Akashi-Kaikyo Bridge. Due to this condition, some bridges are situated at severe environmental condition and subjected to deterioration caused by high chloride intrusion and humidity. Consequently, maintenance and monitoring system must be employed to control the environmental effects and to prevent further deterioration. In the last decade, bridge monitoring has extended its function as an instrument for an efficient stock management. Amid the accumulation of bridge stock and the concentrated construction years, many bridges in Japan are expected to have serious deterioration problems within the next decade. The rush to expand infrastructure during the rapid economy growth has led to cost-cutting by sometimes using minimal materials needed for the structures’ expected performance. Bridges 49

provide an excellent example of the problem. Deterioration is an issue for many highway bridges in Japan, which were mainly built around 1970s. Awareness of the current condition of bridges has emerged recently, triggered by the findings of steel member fractures in the Kisogawa Ohashi Bridge, Mie Prefecture, in June 2007 and in the Honjo Ohashi Bridge, Akita Prefecture, in August 2007. The sudden collapse of the I-35W interstate bridge in Minnesota, United States that followed later in August 2007 has only intensified the concern, considering similarity of the two bridges in Japan with the one that collapse. Many believe these two incidents are the tip of the iceberg of the problem. Adding to the problem of aging bridges is the drastic increase of traffic density. The high intensity and frequency of loading generated by this high traffic volume generates many problems in bridges. The most typical problem is fatigue damage in concrete slabs and steel welded girders. The decrease in maintenance expenditure is expected to continue in the following years due to the budget constraints. Japanese bridge experts now begin to call government’s attention to preventive maintenance of national bridge network. This includes the reevaluation and overhaul of the existing bridge inspection system.

3 CONCEPT OF MONITORING FOR RISK REDUCTION The second part of the paper describes a concept of bridge monitoring as an essential part of risk reduction. To improve bridge safety, monitoring technologies for risk and vulnerability are implemented. Risk is defined as the function of two quantities: hazard and structure vulnerability. Hazard, defined as the probability of occurrence of unexpected events that may endanger the structure, is spatial and temporal dependent. Conventional practice assumes that the structural vulnerability is time-invariant, and a function of structural configuration such as system redundancy, ductility, materials, and quality of construction, all of which are designed at the construction phase. In reality, however, structural vulnerability is also temporal dependent in that it may differ from time to time due to deterioration, aging or changing in environmental and loading conditions. The methodologies for performing hazard analysis and monitoring have been well-developed and are well-established. On the other hand, approaches to quantify a time-variant structural vulnerability are still in under research and development. An example of conventional approach to structural vulnerability assessment is the fragility curves. While useful, the empirical fragility curve is sometimes inadequate due to its limited events and observed damages. Therefore, the analyticalbased fragility curve is developed for a more general use of vulnerability estimation. This approach also has some significant limitations. Since the curve is computed based on a normal distribution assumption, one can never be certain about the exact position of the studied structure in the given distribution. To minimize uncertainties, field monitoring is the feasible option. Using monitoring the actual structure condition can be assessed and therefore its vulnerability can be quantified. To ensure the benefits of monitoring to infrastructure’s stake holders, rationality behind investment made on structural monitoring and its subsequent effects must be clearly presented. A recent study involving the Japan Railway Corporation shows that investment in monitoring for disaster prevention has increased the safety of infrastructure system. It is shown that the benefits of disaster prevention investment in infrastructure do not come immediately but last for longer time. This goes to show that negative impacts may not come immediately even if we do not invest in any disaster prevention measures. However, in the long run, we may suffer from greater consequences. Rapid advances in sensor technology, communication system, and information technology have potential benefits in managing and maintaining an infrastructure system. In recent years, innovations have led to the development of high-tech-based systems that are based on the principle of sensing the structural condition or loading, transferring the measured quantities through communication system to support a knowledgeable decision making. With such advanced systems, large amount of infrastructure can be managed more effectively and potential losses or failures can be minimized. The use of advanced sensor technologies for monitoring is a very important issue for Japan. Considering the increasing number of aged population and decline in the birth rate, it is expected 50

that Japan will face a serious labor shortage in the near future. This problem will also affect the strategy in infrastructure management. In the future, programs that depend extensively on manpower should be avoided, and instead shifted to those that are based on more advanced technologies. There are two fronts of research in monitoring that are currently active, namely sensing technologies, and structural diagnostic/prognostic. The former typically deals with sensor types and systems, data acquisition, data processing, communication, management and storage. The latter deals with data analysis and interpretation, system identification, local and global diagnostic, defect/damage detection and remaining life prediction, all of which are represented by performance indicators. There are two aspects need to be considered when choosing sensor for monitoring civil infrastructure: • Scalability. The civil infrastructure scale is considered on the mesoscale level. Because of the spatial diversity and sheer numbers of structures, the use of a too-expensive and sophisticated microsensing system should be avoided. At the same time, however, the uniqueness of information of each structure system should be retained. • Durability. Civil infrastructures are designed to last for a long time, typically over 50 years. During the service life, hazardous events may not occur very frequently, but nevertheless the monitoring system must be always up and running. This indicates the need for not only reliable but also durable sensors. On the structural diagnostic/prognostic front, the methodologies can be categorized according to the scope and type of analysis. The scope of analysis consists of: (i) microscopic monitoring, where damage detection and localization are of main interest; and (ii) macroscopic monitoring, where holistic structural integrity and its comparison are the main focus. While the microscopic monitoring is the conventional mainstream of structural health monitoring and advancing steadily, macroscopic monitoring is recently attracting interest especially from practical point of view to connect health monitoring and existing inspection methodology.

4 BRIDGE MONITORING: STRATEGIES AND EXAMPLES The third part of the paper outlines strategies implemented for bridge monitoring in Japan. They are categorized into three main groups according to the purpose of monitoring that is for: natural hazard and environment condition, effective stock management, and failure prevention. Examples of bridge monitoring systems that implement these strategies and the lessons learned from monitoring experiences are presented.

4.1 Monitoring for natural disasters: Seismic and wind monitoring Monitoring for environment and natural disasters prevention are described with example of seismic monitoring and wind monitoring. In seismic monitoring, examples are the instrumentation of three long-span cable-supported bridges in Tokyo bay area. The bridges are: Yokohama-Bay Bridge, Rainbow Bridge, and Tsurumi-Fairway Bridge. The instrumentation system and sensor network are presented. Dense seismic measurement systems installed on these bridges are very useful to capture real behavior of the bridge during various levels of earthquake. The study shows that by employing a system identification technique, performance of dynamic characteristics of the bridge can be evaluated. Monitoring for wind-induced vibration is also presented with example of monitoring system employed at Hakucho Bridge. The bridge is situated at a windy area, so that wind load and structural behavior under various wind conditions are of main concern. Owing to detailed measurement and dense sensor deployment, modal characteristics of the bridge can be identified from ambient vibration data. 51

Even though bridge monitoring systems for seismic and wind hazard were initially intended to measure loading, studies presented in this paper indicate the usefulness of these measurements for evaluation of structural integrity. 4.2 Monitoring for stock management In order to realize an efficient stock management, monitoring should be focused on performance evaluation of the condition of the stock. Performance evaluation of a bridge is essential to assess functionality, predict the deterioration and the possible failure mode, update the performance prediction, and decide the future inspection of retrofit plan. For these purposes, new monitoring systems using advanced sensor technologies are expected to improve the conventional inspection procedures. In this section, examples of monitoring for stock management are briefly discussed. They are: a) continuous monitoring of a workhorse bridge; b) Non-contact monitoring system of Shinkansen viaduct by laser Doppler vibrometer; and c) routine inspections of railway and highway by intelligent monitoring system. 4.3 Monitoring for failure prevention Monitoring can also be directed to prevent structural failure. For this purpose, possible failure locations and circumstances under which the failure may occur should be identified a priori. When the failure mode of interest is identified or specified, monitoring system is implemented by selecting the appropriate sensor. Some of failure modes are localized, and so are the locations of sensor. Several such systems are developed and implemented for safety of railway operation. Two examples of monitoring to prevent bridge failure are presented that is prevention of failure due to unseating and the scour-induced collapse detection. Both systems works in such a way that when the failure indicators reach the maintenance limits an alarm is sent to the operator, so that further check and countermeasures can be taken.

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Bridge Maintenance, Safety, Management, Health Monitoring and Informatics – Koh & Frangopol (eds) © 2008 Taylor & Francis Group, London, ISBN 978-0-415-46844-2

Bridging capacity innovations on cable-supported bridges Y.J. Ge & H.F. Xiang Tongji University, Shanghai, China

ABSTRACT: After technical review of the longest cable-supported bridges, the current bridging capacity is summarized as single main span up to 2 km and 1 km together with total deck width about 40 m for suspension bridge and cable-stayed bridge, respectively. Bridging capacity innovations is then introduced with two double main span suspension bridges and one twin parallel deck cablestayed bridge. The special emphasis for double main spans is placed on longitudinal stiffness design of central pylon, and either inversed Y-shaped pylon, in Jiangsu Taizhou Bridge, or I-shaped pylon with fixed connection of deck and central pylon, inAnhui Maanshan Bridge, can provide with proper longitudinal stiffness for central pylon. Two types of pylon and three kinds of deck section have been compared in earlier design stage for twin parallel deck cable-stayed bridge, Ningbo Yongjiang Bridge, and the composite cross section with two diamond pylon has been finally selected with considering structural durability.

1 INTRODUCTION Traditionally, bridging capacity is referring to longitudinal bridge span with the latest records of Akashi Kaikyo suspension bridge and Jiangsu Sutong cable-stayed bridge, and transversal deck width in the current practice about 40 m. Bridging capacity innovation is not invention in making span longer or deck wider, but a further or new development of traditional concepts to make things better in proper way. The concept of continuous multiple main span scheme for crossing longer water body is innovative, and the idea of several parallel bridge deck configuration for providing wider passage way is innovative too. Two suspension bridges with double main spans over 1 km have been launched across Yangtze River in Taizhou, Jiangsu Province, and Maanshan, Anhui Province. Among several under designed cable-stayed bridges with twin parallel decks, Ningbo Yongjiang Bridge has the longest central span of 468 m. Taking as these three examples, special structural characteristics and practical implications related to double main spans or twin parallel decks are revealed and discussed in the following sections.

2 DEVELOPMENT OF BRIDGING CAPACITY 2.1 Steel-chain suspension bridges Although ancient suspension bridges were built in iron chain in China long before the history of steel application in the 19th century, the construction of modern steel-chain suspension bridges around the world has experienced a considerable development for more than a century. It took about 54 years for the span length of suspension bridges to grow from 483 m of Brooklyn Bridge in 1883 to G. Washington Bridge and to 1,280 m of Golden Gate Bridge in 1937, and had an increase by a great factor of about 2.7. Although the further increase in the next 44 years from Golden Gate Bridge to Verrazano Bridge and to Humber Bridge of 1410 m in 1981 was only 10% or by a factor of 1.1, another factor of about 1.4 was realized in Akashi Kaikyo Bridge with a 1,991 m main span 53

Figure 1.

1080 m + 1080 m Double main-span suspension bridge (Anhui Maanshan Bridge).

within 17 years in 1998. It is probably correct to conclude that modern suspension bridge practice has provided with a traditional three-span bridging configuration with single main span up to 2 km and total deck width of 40 m for six traffic lanes. 2.2 Modern cable-stayed bridges Cable-stayed bridges can be traced back to the 18th century, and many early suspension bridges were of hybrid suspension and cable-stayed construction, for example, Brooklyn Bridge in 1883. One of the first modern cable-stayed bridge is a concrete-decked cable-stayed bridge built in 1952 over the Donzere-Mondragon Canal in France, but it had little influence on later development. The steel-decked bridge, Stromsund Bridge in Sweden by Franz Dischinger in 1955, is therefore more often cited as the first modern cable-stayed bridge with a main span of 183m. It took about 31 years for the span length of cable-stayed bridges to increase to 465 m in Annacis Bridge in Canada in 1986, but in the last decade of the past century, the span length grew very rapidly, from 520 m of Skamsund Bridge in 1991, to 602m of Yangpu Bridge in 1993, then to 856 m of Normandy Bridge in 1995 and finally to 890 m of Tatara Bridge in 1999. Another big jump with about two hundred meters in span length has been realized in Jiangsu Sutong Bridge with the 1088 m length of main span in this year. Based on the bridging capacity figures, we may dare say that recent development of cable-stayed bridges has ensured the bridging capacity of a 1 km long main span and 40 m wide bridge deck for six traffic lanes. 3 DOUBLE MAIN SPAN SUSPENSION BRIDGES 3.1 Conceptual comparison of single and double main-spans In order to make the conceptual comparison of a double main-span suspension bridge and the corresponding single main-span structure, Anhui Maanshan Bridge has been taking as a typical model of a double main-span suspension bridge, with the span arrangement of 360 + 1080 + 1080 + 360 m and the sag to span ratio of main cable of 1/9, shown in Fig. 1. The corresponding comparison model is a traditional three-span suspension bridge of 720 + 2160 + 720 m, and has the same sag to span ratio of 1/9. With the same steel box deck, these two bridge models have been investigated with different schemes of pylon stiffness as follows: Scheme A-1: Single main-span structure with infinite stiffness pylons Scheme A-2: Single main-span structure with proper stiffness pylons Scheme B-1: Double main-span structure with infinite stiffness pylons Scheme B-2: Double main-span structure with proper stiffness side pylons and infinite stiffness center pylon Scheme B-3: Double main-span structure with proper stiffness pylons Having performed a dynamic finite-element analysis, the first and second natural frequencies of the structures have been extracted and compared for these five schemes in Table 1. The first and second frequencies of the double main-span scheme (B-1) are tremendously enhanced comparing with the single main-span scheme (A-1) under the condition with infinite stiffness pylons, and the increase factors are 2.51 and 1.27 in the first and second lateral bending frequencies, 1.18 and 1.08 in the first and second vertical frequencies, and 2.11 and 1.88 in the first and second torsional 54

Table 1. The first and second natural frequencies. Lateral bending (Hz)

Vertical bending (Hz)

Torsional vibration (Hz)

Scheme

First

Second

First

Second

First

Second

A-1 A-2 B-1 B-2 B-3

0.0367 0.0363 0.0923 0.0922 0.0922

0.0768 0.0765 0.0973 0.0971 0.0969

0.1016 0.0960 0.1195 0.1194 0.0828

0.1466 0.1283 0.1590 0.1553 0.1196

0.1789 0.1788 0.3780 0.3347 0.2634

0.2045 0.1998 0.3836 0.3610 0.3355

frequencies. This is the most important reason why a double main-span suspension bridge is better in structural dynamic performance than the corresponding single main-span structure. 3.2 Longitudinal stiffness optimization of central pylon 3.2.1 Decisive factors of longitudinal stiffness selection As concluded in the previous section, the most important structural characteristic is probably the longitudinal bending stiffness of a central pylon, Rp , defined as

where T1 and T2 = cable forces at the central pylon top; α1 and α2 = the cable angles at the central pylon top; and δp = longitudinal displacement of the central pylon top. Under the most unfavorable load condition, only one main span being loaded, the longitudinal bending stiffness of a central pylon dominantly controls bridge structure performance including displacements and stresses of central pylon and deck as well as sliding resistance between main cable and saddle pad. Accordingly, the selection of the longitudinal stiffness of central pylon should carefully check with four decisive factors as follows. (1) δd = Vertical displacement of the mid-span deck, which steadily decreases with the increase of the longitudinal stiffness of central pylon, Rp . (2) δp = Longitudinal displacement of the central pylon top, which also decreases with the increase of the longitudinal stiffness of central pylon, Rp . (3) σm = Maximum or minimum working stresses in central pylon, which increases with the increase of the longitudinal stiffness of central pylon, Rp . (4) Ks = Safety factor of sliding resistance between main cable and saddle pad, which decreases with the increase of the longitudinal stiffness of central pylon, Rp , and can be defined as,

where µ = friction factor between main cable and saddle pad, and µ = 0.2 based on various experiments; and θ = angle of saddle arc. According to the current design code for highway suspension bridges in China, the value of Ks should be greater than 2. 3.2.2 Limit types of central pylon for longitudinal stiffness With the aspect of longitudinal bending stiffness, longitudinal shapes of central pylons can be broadly divided into two limit types, A-shaped central pylon with the greatest stiffness described in Fig. 2a and I-shaped central pylon with the smallest stiffness described in Fig. 2b. With adopting a A-shaped central pylon (Fig. 2a), by which the longitudinal bending stiffness of a central pylon is relatively large, the vertical displacement at the mid-span deck and the longitudinal displacement at the central pylon top will be relatively small, but the safety factor of sliding resistance and the 55

Figure 2.

Longitudinal shapes of central pylon.

Figure 3.

General layout of Jiangsu Taizhou Bridge.

maximum and minimum stresses in a centre pylon will be relatively unfavorable. Otherwise, with using I-shaped central pylon (Fig. 2b), by which the longitudinal stiffness is relatively small, the deck and pylon displacement will be relatively large, and the sliding safety factor and the pylon’s stresses will be relatively favorable. Taking as an example, Jiangsu Taizhou Bridge, 2940 m in total length, consists of four spans including double 1,080 m main spans and two side spans of 390 m shown in Fig. 3. In order to select an appropriate stiffness of a central pylon, both A-shaped steel pylon and I-shaped concrete pylon with various stiffness values had been firstly compared and contrasted through structural analysis. Based on the critical value of Ks ∼ = 2.00, the longitudinal bending stiffness of central pylon, Rp , should be kept at about 25 to 26 MN/m. It can be found that the working stresses are very high (σmax = 296 MPa and σmin = −200 MPa) in A-shaped steel pylon, and the cross sections are very large (6 × 6 m at the top and 12 × 10 m at the bottom) in I-shaped concrete pylon. 3.2.3 Optimal longitudinal stiffness and related characteristics Combined with the advantages of both types ofA-shaped steel pylon and I-shaped concrete pylon, an optimal shape of central pylon, inversed Y-shaped steel pylon shown in Fig. 2c, was then proposed. The longitudinal stiffness of this type of central pylon is mainly depended upon the spacing w and the height h1 of two legs, and the calculation with different combinations of w and h1 has also been performed. The longitudinal stiffness is about 26 MN/m, which is realized by providing the spacing w = 36 m and the height h1 = 72 m of two legs, and the maximum and minimum working stresses are equal to 245 MPa and −134 MPa, which are 37% and 61% reduced from those of A-shaped pylon, respectively. Therefore, the inversed Y-shaped steel pylon was chosen as the final scheme of the central pylon. With the final scheme of central and side pylons, the static analysis with the finite element model of Jiangsu Taizhou Bridge has been conducted in various load combinations, and the main calculation results of the most critical combination, dead load plus live load applied in one main span, are shown in Table 2. 56

Table 2. Calculation results under dead load plus live load applied in one main span in Taizhou Bridge. Longitudinal displacement at the top (m) Applied force at the central pylon top (MN) Maximum vertical displacement of deck (m) Main parameters of sliding resistance Working stresses in steel central pylon

Side pylon loaded Central pylon Side pylon unloaded 0.194 1.876 0.022 Loaded-side cable force Unloaded-side force Longitudinal shear force 183.9 170.8 9.84 Upward Downward Summation 3.200 4.352