Integral and Semi-integral Bridges Martin P. Burke Jr. PE
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Integral and Semi-integral Bridges Martin P. Burke Jr. PE
A John Wiley & Sons, Ltd., Publication
Integral and Semi-integral Bridges
Dedication
This work is affectionately dedicated to the memory of my father, Martin P. Burke Jr. of Pittsburgh, Pennsylvania. After I was born, he became known as Big Mart. But even when I grew a head taller than him, his associates, friends, and acquaintances continued to refer to and speak of him as Big Mart. Both they and I knew that they were thinking and speaking about the right person. And they were using the right name.
Integral and Semi-integral Bridges Martin P. Burke Jr. PE
A John Wiley & Sons, Ltd., Publication
This edition first published 2009 © 2009 Martin P. Burke Jr. Blackwell Publishing was acquired by John Wiley & Sons in February 2007. Blackwell’s publishing programme has been merged with Wiley’s global Scientific, Technical, and Medical business to form Wiley-Blackwell. Registered office John Wiley & Sons Ltd, The Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, United Kingdom Editorial offices 9600 Garsington Road, Oxford, OX4 2DQ, United Kingdom 2121 State Avenue, Ames, Iowa 50014-8300, USA For details of our global editorial offices, for customer services and for information about how to apply for permission to reuse the copyright material in this book please see our website at www.wiley.com/wiley-blackwell. The right of the author to be identified as the author of this work has been asserted in accordance with the Copyright, Designs and Patents Act 1988. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, except as permitted by the UK Copyright, Designs and Patents Act 1988, without the prior permission of the publisher. Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic books. Designations used by companies to distinguish their products are often claimed as trademarks. All brand names and product names used in this book are trade names, service marks, trademarks or registered trademarks of their respective owners. The publisher is not associated with any product or vendor mentioned in this book. This publication is designed to provide accurate and authoritative information in regard to the subject matter covered. It is sold on the understanding that the publisher is not engaged in rendering professional services. If professional advice or other expert assistance is required, the services of a competent professional should be sought. Library of Congress Cataloging-in-Publication Data Burke, Martin P. Integral and semi-integral bridges / Martin P. Burke. p. cm. Includes bibliographical references and index. ISBN 978-1-4051-9418-1 (hardback : alk. paper) 1. Concrete bridges—Design and construction. 2. Concrete bridges—Joints. I. Title. TG340.B88 2009 624.2—dc22 2009006791 A catalogue record for this book is available from the British Library. Set in 10/12 pt Minion by SNP Best-set Typesetter Ltd., Hong Kong Printed in Singapore 1
2009
Contents
Acknowledgments Introduction
vii xi
Chapter 1
Integral Bridges
Chapter 2
Bridge Damage and the Pavement G/P Phenomenon
21
Chapter 3
Integral Bridges: Attributes and Limitations
41
Chapter 4
Design of Integral Bridges: A Practitioner’s Approach
59
Chapter 5
Genesis of Integral Bridges
71
Chapter 6
Cracking of Concrete Decks and Other Problems with Integral-type Bridges
81
Integral Bridge Design in the Land of No Special Computations
99
Chapter 7
1
Chapter 8
Semi-integral Bridges: Movements and Forces
121
Chapter 9
Emergence of Semi-integral Bridges
139
Chapter 10
Elementalistic and Holistic Views for the Evaluation and Design of Structure Movement Systems
157
Awareness of Reality in Bridge Design
185
Appendix 1 The Pavement Growth/Pressure Phenomenon: The Neglected Aspect of Jointed Pavement Behavior
215
Appendix 2 Glossary
243
Appendix 3 Captions for Photographs
245
Index
247
Chapter 11
v
Acknowledgments
Grateful acknowledgment is made to the publishers of the papers identified below for their permission to use all or parts of them for the various chapters of this book. It should be understood that such permission does not constitute endorsement by the publishers of any statement, method, or practice given or recommended. These have been and must be the full responsibility of the author. However, it should also be understood that those who interpret and implement the opinions and advice given in this book do so with the realization of their complete responsibility for such interpretation and implementation. The author has been diligent in his efforts to avoid errors and to eliminate inconsistencies in this work. However, if and where he has failed, he would appreciate being informed by readers so that this work can be appropriately revised for possible later editions. Chapter 1: Transportation Research Board of the National Academies, Washington, D.C., for “Integral Bridges,” from Transportation Research Record: Journal of the Transportation Research Board (Transportation Research Record) No. 1275, 1990, pp. 53–61. Also, Ohio Department of Transportation, for “Integral Bridges – Development and Design,” Proceedings, Ohio Transportation Engineering Conference, Columbus, Ohio, 1989. Chapter 2: American Concrete Institute, Farmington Hills, Michigan, for “Reducing Bridge Damage Caused by Pavement Forces,” from Concrete International, January, 2004, Vol. 26, No 1, pp, 53–57, and February, 2004, Vol. 26, No. 2, pp. 83–89. Chapter 3: Transportation Research Board of the National Academies, Washington, D.C., for “Integral Bridges: Attributes and Limitations,” from Transportation Research Record, No. 1393, 1993, pp. 1–8. Chapter 4: American Concrete Institute, Farmington Hills, Michigan, for “Design of Integral Concrete Bridges: A Practitioner’s Approach,” from Concrete International, June, 1993, Vol. 15, No. 6, pp. 37–42. Chapter 5: American Concrete Institute, Farmington Hills, Michigan. for “Genesis of Integral Bridges in Ohio,” from Concrete International, July, 1996, Vol. 18, No. 7, pp. 48–51. Chapter 6: Transportation Research Board of the National Academies, Washington, D.C., for “Cracking of Concrete Decks and Other Problems with Integral-Type Bridges,” from Transportation Research Record No. 1688, 1999, pp. 131–138. Chapter 8: Transportation Research Board of the National Academies, Washington, D.C., for “Semi-Integral Bridges: Movements and Forces,” from Transportation vii
viii
Acknowledgments
Research Record No. 1460, 1994, pp. 1–7. Also, Spon Press for “Semi-Integral Bridges: A Concept whose Time Has Come,” from Continuous and Integral Bridges, 1994, pp. 213–224. Chapter 9: Transportation Research Board of the National Academies, Washington, D.C., for “Emergence of Semi-Integral Bridges,” from Transportation Research Record No. 1594, 1997, pp. 179–186. Also, Charles S. Gloyd co-author of “The Emergence of Semi-Integral Bridges.” Chapter 10: Transportation Research Board of the National Academies, Washington, D.C., for “Structure Movement Systems Approach to Effective Bridge Design,” from Transportation Research Record No. 1594, 1997, pp. 147–153. Chapter 11: Engineers’ Society of Western Pennsylvania, Pittsburgh, Pennsylvania, for “Awareness of Reality in Bridge Design,” Proceedings, 11th International Bridge Conference, 1994, pp. 271–283. Appendix 1: Transportation Research Board of the National Academies, Washington, D.C., for “Pavement Pressure Generation: Neglected Aspect of Jointed Pavement Behavior,” from Transportation Research Record No. 1627, 1998, pp. 22–28. This work would not have been possible without the original encouragement and assistance the author received from: the executives and staff members of Burgess and Niple, Engineers and Architects (B&N); the many professional colleagues of the General Structures Committee of the Transportation Research Board of the National Academies who reviewed and critiqued the original papers that formed the basis for the present work; and the many individuals and organizations from throughout the United States and abroad (some of whom are identified below) who graciously responded to the author’s requests by contributing comments, data, drawings, and photographs that were used herein as figure illustrations. The author greatly appreciates the assistance of Anthony Allbery, Dan Landbo, and Chris Carlisle of B&N who helped to prepare some of the drawings used to illustrate this work. The author would also like to take this opportunity to recognize the original structure conceptions and evolutionary contributions made by his many deceased professional mentors and colleagues of the Ohio Department of Transportation, and by the chief engineers of the Washington State and Tennessee Departments of Transportation. Over the years, they and he have shared the same concerns that motivated the origination and development of integral and semi-integral bridges. These tough and durable little bridges are now not only serving many of the nation’s state transportation systems, but also beginning to serve the transportation systems of other nations as well. If it were possible, they would be pleased to learn that their bridge pioneering efforts have had such huge and beneficial consequences. Cover: Edward P. Wasserman and photographer George Hornel, Tennessee Department of Transportation. Introduction: Paul Kinderman, Washington State Department of Transportation (photograph). Chapter 1: Edward P. Wasserman and photographer George Hornel, Tennessee Department of Transportation (photograph and Figure 1.3).
Acknowledgments
ix
Chapter 2: Dennis W. Heckman, Missouri Department of Transportation (photograph); Jack Mecklenborg (Figure 2.1); William Detrict, Indian Department of Transportation (J. F. K. Bridge data); Paul Hasselquist, Ted Barber and Jimmy Camp, New Mexico Department of Transportation (Figures 2.5 and 2.6); Shakir Shatnawi, California Department of Transportation (Figure 2.8d). Chapter 3: Yuqiao Yang, photographer (photograph). Chapter 4: East Nippon Expressway Company Ltd., with all rights reserved (photograph). Chapter 6: Jai Lee, B&N (photograph); I. H. P . J. Taylor, Tarmac Precast Concrete Ltd, UK (Figures 6.5 and 6.6). Chapter 7: I. H. P. J. Taylor, Tarmac Precast Ltd, UK (photograph); Bruce Ford, City of Akron, Ohio, (Figure 7.1); Mitch McCoy, McCoy Associates (Figure 7.3). Chapter 8: Greg Baird, courtesy of Ohio Department of Transportation (photograph and Figure 8.6). Chapter 9: Marc C. Eberhard, University of Washington State (photograph). Chapter 10: Dale Poorman, B&N (Figures 10.11 and 10.12). Chapter 11: Ronald K. Mattox, Gresham, Smith Partners (photograph); Marc C. Eberhard, University of Washington State (Figure 11.8); 1832 Drawing by Charles Graham (Figure 11.12, upper right); Pittsburgh Post Gazette, 2008, Copyright, all rights reserved. Reprinted with permission (Figure 11.12, middle left); Carnegie Library of Pittsburgh (All rights reserved. Unauthorized reproduction or usage prohibited.) (Figure 11.12, middle right); Greg Panza, Mount Washington Community Development Corporation, Pittsburgh (Figure 11.12, bottom). Appendix: 1: John Charman, courtesy of the Highways Agency, UK (photograph); Les Hawker, courtesy of the Highways Agency, UK (Figure A1.4); Toronto Star newspaper and photographer Paul Regan (Figures A1.5 and A1.9). Appendix 2: Bala Tharmabala and Sean Morris, Ontario Ministry of Transportation (photograph).
Introduction The final success of our journey through life depends upon how much we are willing to learn from others. There is not time enough in a lifetime to learn from our own experience alone everything we need to know. A. B. ZuTavern
Captions for the first page photograph of each section of this book are given in Appendix 3.
This book is not a primer on the analysis, design, and construction of continuous bridges, or on the design of many of the common components of integral and semi-integral bridges, components that are typical of all deck-type highway bridges. These subjects are described and discussed in many excellent textbooks that have been developed and published by others especially for that purpose. Rather, this book focuses on those subjects that are of significance for the design and construction of integral and semi-integral bridges, subjects that generally are not described and discussed elsewhere. In brief, these subjects include but are not limited to the following: Chapter 1: The evolution of deck-type highway bridges in the United States is traced from the jointed single-span bridges of the early 1930s to the fully integral bridges of the late 1990s. Also described are a few recent examples of the conversion of existing jointed bridges to integral types of construction. Chapter 2: The uncontrolled G/P (growth/pressure) phenomenon is probably responsible for more pavement and bridge damage than any other cause with xi
xii
Introduction
the exception of de-icing chemical deterioration. Yet its cause and its characteristics are not familiar to most bridge design engineers and bridge administrators. This chapter describes the effect of this phenomenon on three different bridge types. These examples are given as a warning of similar damage that may be sustained by other bridges unless the phenomenon is controlled, or unless more compressive-resistant integral or semi-integral bridges are built instead of the more pressure-vulnerable jointed bridges. Chapter 3: An elaboration about the many attributes and few limitations of integraltype bridges is given that should be considered not only in evaluating the suitability of integral bridges for particular applications but also during their design and construction. Chapter 4: Analysis and design procedures and research findings that form the basis for a pragmatic bridge design engineer’s approach to the design of a limited range of integral bridges are discussed. Some of the primary and secondary stresses that affect these structures are also discussed, including shrinkage, creep, passive pressure, settlement, thermal gradients, buoyancy, earthquakes, etc. Chapter 5: As strange as it may seem, the conceptual background developed for large deck-type, open-spandrel, rib-arch bridges appears to have been the primary inspiration for the design and construction of the 1938 Teens Run Bridge of Gallia County, Ohio, the first fully integral deck-type highway bridge constructed in the United States. This chapter documents the early concerns and design decisions that resulted in the design and construction of this remarkable little historic structure. Chapter 6: Although integral and semi-integral deck-type highway bridges are simple in concept and easy to construct, there are enough structural differences between them and their jointed counterparts that some unique problems arise, especially during construction, which generally are not anticipated by those building them for the first time. This chapter describes some of these problems so that they can be anticipated and prevented. Chapter 7: This chapter describes the “Land of No Special Computations.” It also describes some of the various problem-solving techniques used by pragmatic bridge design engineers to achieve successful bridge designs in the Land of No Special Computations. These techniques become particularly important when considering the significance of secondary stresses during the analysis and design of typical integral bridges. Chapter 8: During the expansion of skewed integral and semi-integral bridges, their superstructures are progressively forced to rotate in a horizontal plane toward their acute corners. This chapter describes this behavior and provides a simplified procedure for estimating the magnitude of the forces involved; it also describes how these forces can be suitably and economically resisted. Chapter 9: In 1977, this author developed the first semi-integral bridge design for the Ohio Department of Transportation. At that time it was presumed that this bridge was the first of its kind constructed in the United States. Subsequently, it was learned that other bridges based on the same general concept had preceded it by many years. Apparently, bridge engineers of several other states had independently devised and built a few of their own versions of this unusual concept. One of them, Willis B. Horne of Washington State, devised his own version more
Introduction
xiii
than a decade before Ohio’s, and his State had been using this basic concept (in place of integral bridges) for most of its typical highway bridge applications. This chapter identifies these other states and provides detail sketches of their semiintegral designs and commentary about their design practices. Chapter 10: The structure movement systems approach to the design of highway bridges is described and illustrated. This is the approach that is used by bridge design engineers with the most experience with integral and semi-integral bridges. It describes how integral and semi-integral bridge applications (or, for that matter, all highway bridge applications) are or can be conceptualized holistically as composite structures, structures that are conceived to be composed of various types of structure movement systems. It also describes how the use of this holistic approach during design can aid design engineers avoid many of the design mistakes that are made by their less experienced and elementalistically oriented and limited colleagues and predecessors. Chapter 11: During a bridge replacement and bridge rehabilitation project for the State of Ohio, a project that consisted of over 1,800 bridges designed by over 80 small consulting engineering firms, it soon became evident that many of the designers working on this project seem to have a predilection towards particular types of design errors. This chapter describes some of these and other errors, and speculates that certain common aspects of an individual’s early education and continued academic conditioning resulted in an orientation that could be described as a general lack of awareness. Appendix 1: This appendix contains a critique of unfortunate concrete pavement recommendations originating from a Midwest State Department of Transportation and a few misguided published recommendations of a certain pavement research “specialist.” These unfortunate recommendations appear to suggest that those making them were not fully knowledgeable about the characteristics of the G/P phenomenon or its destructive potential. The chapter also provides a brief but sufficient description of this destructive phenomenon, and contains rather extensive documentation of some of the pavement and bridge damage associated with the phenomenon. Appendix 2: This is a glossary prepared to aid novice engineers encountering some of the subjects discussed in this book for the first time. Possibly, if others accept these definitions, they may also be found useful for clarifying their own discussions of the same or similar subject matter. Appendix 3: This appendix contains bridge data for and descriptions of the integral and semi-integral bridges shown in photographs that appear on the first page of each section of this book. Typically, these bridges are unique examples of integral and semi-integral bridges (the first of its kind, the longest span, the greatest curvature, etc.) that have been constructed in the United States, United Kingdom, Canada, Japan, and Korea. Hopefully, photographic images of similar bridges constructed in other states and countries will become available for future editions of this book.
Chapter 1
Integral Bridges
We are suspicious of new ideas, however good, if they threaten old ideas however bad. Frank A. Clark
Introduction The first integral bridge in the United States was the Teens Run Bridge. It was built in 1938 near Eureka in Gallia County, Ohio. It consists of five continuous reinforced concrete slab spans supported by capped pile piers and abutments. Since that time construction of integral bridges has spread throughout the United States and abroad. The United Kingdom recently adopted them for routine applications. Japan completed its first two in 1996. South Korea completed its first such bridge in 2002. Integral bridges may be briefly defined as single-span or continuous multiplespan bridges constructed without movable transverse deck joints (movable deck joints) at piers or abutments, or as more generally described in Chapter 10 and Appendix 2, integral bridges may be conceived of as components of composite structure movement systems, systems generally composed of: 1
2
Integral and Semi-integral Bridges
• • • • •
Jointless superstructures constructed integrally with capped pile abutments Abutments supported by embankments and single rows of vertically driven piles Rigid piers with movable bearings, or flexible piers constructed integrally with the superstructure Attached approach slabs that bear on abutments and abutment backfill Cycle control joints, of some sort, for the longer bridges, located between approach slabs and approach pavements.
When multiple-span bridges are constructed without movable deck joints at piers, it is accepted that the continuity achieved by such construction will subject superstructures to secondary stresses, stresses that are induced by the response of continuous superstructures to settlements of substructures, post-tensioning, etc. When continuous bridges are constructed without such joints at the superstructure/ abutment interface, it is likewise accepted that they will, in addition, be subjected to secondary stresses due to superstructure/abutment continuity, and to the resistance of abutment foundations and backfill to cyclic longitudinal superstructure movements. The justification for such construction is based on the growing awareness that, for single- and multiple-span bridges of moderate lengths, significantly more damage and distress have been caused by the use of movable deck joints at piers and abutments than the secondary stresses that these joints were intended to prevent. In addition, elimination of costly joints and bearings and the laborintensive details and construction procedures necessary to permit their use have generally resulted in more cost-effective bridges. Consequently, more and more bridge engineers are now willing to relinquish some of their control of secondary stresses primarily to achieve simpler and more cost-effective bridges and bridges with greater overall integrity and durability. Before continuing this discussion about integral bridges, a pause should be taken here to comment on the use of the unfortunate phrase “integral abutment bridges.” It is this author’s contention that the use of this phrase by members of the bridge engineering profession leaves novice engineers with the incorrect impression that it would be proper and acceptable to provide integral abutments for all bridges including multiple-span non-continuous bridges. Obviously, such construction is totally inappropriate, and especially for those projects that are built in conjunction with jointed concrete approach pavement (see Chapter 2). It therefore should be understood that in this and other chapters of this book, the designations “integral bridges” and “semi-integral bridges” will be used exclusively. The first designation refers to single- or multiple-span continuous bridges without movable deck joints at the superstructure/abutment interface. These are generally supported by embankments with stub-type abutments on flexible piles. The second designation refers to single- or multiple-span continuous bridges without movable deck joints in their superstructures but with movable longitudinal joints between their superstructures and rigidly supported abutments. The piers for such structures may be semi-rigid self-supporting structures generally surmounted by movable bearings, or flexible substructures constructed integrally with superstructures. Approach slabs that span across and are partially supported by structure backfill should be attached to the superstructures of such bridges. Cycle-control joints (see Appendix
Chapter 1
Integral Bridges
3
2) in some form should be provided between their approach slabs and approach pavements.
Continuous superstructures Current design trends (about 1990) received their primary impetus and direction almost six decades ago. In May 1930, a brief 10-page paper on the “Analysis of Continuous Frames by Distributing Fixed End Moments” [1], published in the Proceedings of the American Society of Civil Engineers, generated considerable discussion in academia. Its publication was followed shortly by what could be considered a minor revolution in the design and construction of short- and moderate-span bridges. In that paper, Professor Hardy Cross presented a simple and quick method for the analysis of integral-type structures such as continuous beams and frames. His moment distribution method was quickly adopted by bridge design engineers, and the bridge design and construction practices of many transportation departments began to change. Before Cross’s “Moment Distribution” [1], most multiple-span bridges were generally constructed as a series of simple spans. Following the introduction of moment distribution, bridge design engineers began adopting continuous construction primarily to eliminate troublesome movable deck joints at piers. On the basis of a nation-wide mail survey of state and province transportation departments [2], it appears that the Ohio Highway Department (now the Ohio Department of Transportation, or Ohio DOT) was one of the first agencies to initiate the routine use of continuous construction for the design and construction of multiple-span bridges. Its experience provides an informative background for this movement toward the use of fully integrated construction. To minimize the use of movable deck joints at piers and thus prevent deleterious deck drainage from reaching and saturating the surfaces of vulnerable primary superstructure and pier components, beginning in the late 1920s and early 1930s, Ohio DOT adopted the routine use of continuous construction for multiple-span highway bridges. To make such a practice possible at a time when continuous construction was a rarity, Ohio DOT had to develop and perfect various field-splicing procedures for the bridging materials then available. For the shortest multiple-span bridges and those bridges with spans less than 50 ft. (15 m), continuous reinforced concrete slab bridges were developed and adopted. At first, rolled steel beams were made continuous by the use of riveted field splices at piers (Figure 1.1). To achieve continuous steel girders, field-riveted plate and angle splices were provided at counter flexure points. At about the same time, welding procedures and welder pre-qualification tests were developed for field welding of steel bridge members, and some of the shortest rolled beam bridges were provided with field-welded splices at piers. These initial welded splices consisted of partially butt-welded beam webs supplemented with fillet-welded moment plates. Field-welded splices were constantly being improved by Ohio DOT and, by the mid-1950s, all rolled beam bridges were being made continuous by field butt welding of beam webs and flanges, and by fillet welding of flange moment plates. From the late 1920s to the mid-1950s, steel girder fabrication and girder field splices were of riveted construction. However, in 1954, high-strength bolts were used
4
Integral and Semi-integral Bridges
Figure 1.1 USR 52, Isaacs Creek Bridge, Adams County, Ohio, 1931. This was one of first steel beam bridges in Ohio where riveted field splices at piers were used to achieve superstructure continuity.
in lieu of field-driven rivets for the field splices of the Patterson-Riverside, Great Miami River Bridge of Dayton, Ohio (Figure 1.2). This was one of the first applications of high-strength bolting for highway bridges in the United States. By 1963, high-strength bolting replaced field butt welding in Ohio as the method of choice for integrating multiple-span bridges to achieve full continuity. Consequently, by riveting, field butt welding, and high-strength bolting, Ohio DOT has employed continuous construction for more than 70 years. In conjunction with the development and adoption of continuous construction for all moderate-length highway bridges, Ohio DOT was also the first state to routinely eliminate deck joints at abutments. This was accomplished in the case of continuous reinforced concrete slab bridges by providing embankments and stubtype integral abutments supported by flexible piles in lieu of movable deck joints and wall-type abutments (see Chapter 5). This new abutment type is now designated as an integral abutment and Ohio DOT was the first state transportation department to adopt such construction as a standard practice. A version of this integral abutment design has been used in Ohio for many hundreds of bridges ever since. However, it was not until the early 1960s that the integral concept was first used by Ohio DOT for a steel beam bridge (see Appendix 3, photograph). Since that time, most steel beam and girder bridges with skews 30 ° or less, and lengths not longer than about 300 ft. (91.44 m), were of integral construction (if site geological characteristics and/or embankment heights allowed the use of flexible piles for abutment support). In 1951, Ohio DOT was one of the first transportation organizations in the United States to pioneer the use of prestressed concrete for highway bridges. In fact,
Chapter 1
Integral Bridges
5
Figure 1.2 The Patterson-Riverside, Great Miami River Bridge, Dayton, Ohio, 1954.
Ohio DOT set up its own plant for casting and prestressing concrete T-beams. More than a dozen single-span bridges were constructed using these state-manufactured, prestressed concrete beams. But it was not until the early 1960s that commercially produced, prestressed box beams were adapted to continuous construction. These first continuous, prestressed box beam bridges were also provided with embankments and stub-type abutments on flexible piles but they were not entirely jointless because rotation joints were provided at abutments. Recently, however, some fully integral, continuous, prestressed box beam bridges were built by Ohio DOT. Two design examples serve to illustrate just how strongly Ohio DOT bridge engineers favored the use of integral bridges, and the unusual means that they were willing to consider just to avoid the use of movable deck joints in highway bridges. For instance, at some sites where the depth of overburden was not considered sufficient to provide flexible piles for integral abutment construction, bedrock has been prebored and backfilled to a suitable depth to permit the driving of end-bearing flexible piles for the abutments. At other sites, stream channel alignments have been modified so that integral bridges could be used that would not exceed the 30 ° skew limitation that had been established for such structures. As can be surmised by these examples, and the other practices that have been developed and adopted by Ohio DOT, Ohio bridge design engineers’ primary bridge design goal has always been the avoidance of deck joints whenever practicable. Somewhat paralleling Ohio DOT’s implementation of continuous construction, other state and province transportation departments were also showing interest in similar construction. By 1987, 26 out of 30 mail responses [2, p. 20], or 87 percent of responding transportation departments, indicated that they were using continuous construction for short- and moderate-length bridges.
6
Integral and Semi-integral Bridges
Figure 1.3
Long Island Bridge, Kingsport, Tennessee, 1980.
The Tennessee Department of Transportation (Tennessee DOT) now appears to be leading the way in the construction of continuous bridges. For example, the Long Island Bridge of Kingsport, Tennessee (Figure 1.3) was constructed in 1980 using 29 continuous spans without a single intermediate movable deck joint. The total length of this bridge is about 2,700 ft. (823 m) center to center of abutment bearings. Movable deck joints and movable bearings were furnished, but only at the two abutments. It has aptly been named the “Champ.”
Integral bridges During the last half-century, many bridge engineers have become acutely aware of the relative performance of bridges built with and without movable deck joints. In this respect, bridges without such joints (integral bridges) have performed more effectively because they remain in service for longer periods of time with only moderate maintenance and occasional repairs. Some of this experience was forced upon bridge engineers by circumstances beyond their control. As a result of the growth and pressure generated by jointed rigid pavement (see Chapter 2 and Appendix 1), many bridges built with movable deck joints have been and are being severely damaged. After these joints are closed by pavement growth, the effectively jointless bridge restrains the pavement from further growth, resulting in the generation of longitudinal pavement pressures (compressive forces) against and within the bridge. Over time, these pavement pressures can easily exceed
Chapter 1
Integral Bridges
7
1000 psi (6.89 MPa) or cumulatively the total force due to such pressures can exceed 650 tons (716 tonnes) per lane of approach pavement [3]. When the design of abutments of non-integral-type bridges – bridges with movable deck joints at the superstructure/abutments interface – is considered, forces of these magnitudes are irresistible. Stub abutments subjected to such pressures have routinely been moved, joints closed, and ultimately joints and wingwalls fractured. Wall-type abutments have been split from top to bottom. In longer bridges with intermediate movable deck joints, piers have been cracked and fractured as well (see Chapter 2). In geographical regions of the country that experience low seasonal temperatures and an abundance of snow and freezing rain, the use of de-icing chemicals to maintain dry pavements throughout the winter season has also had a significantly adverse affect on the durability and integrity of bridges built with movable deck joints. Open joints and sliding plate joints of shorter bridges and open finger joints of longer bridges have allowed roadway drainage, contaminated with de-icing chemicals, to penetrate below roadway surfaces and wash over supported beams, bearings, and bridge seats. The resulting corrosion and deterioration have been so serious that some bridges have collapsed while others have had to be closed to traffic to prevent their collapse. Many jointed bridges have required extensive repair. Most of the jointed bridges that have remained in service have required almost continuous maintenance to counteract the adverse effects of contaminated deck drainage. To help minimize or eliminate these maintenance efforts, a whole new industry was born. Beginning in the early 1960s, the first elastomeric compression seals were installed in bridges in the United States to seal movable deck joints. Since these first installations, numerous types of elastomeric joint seals have been developed and improved in an attempt to achieve joint seal designs that would both effective and durable. Most designs have been disappointing. Many leaked. Some required more maintenance than the original bridge built without them. By and large, the many disappointments associated with various types of joint seals have caused bridge engineers to consider other options. Costs of various types of bridges show marked differences. For two bridges built in essentially the same way, except where that one was provided with movable deck joints at the superstructure/abutment interface and the other with integral abutments, the jointed bridge was usually the more expensive. In addition, abutments of integral bridges suffered only minor damage from pavement pressure, were essentially unaffected by de-icing chemicals, and functioned for extended periods of time without appreciable maintenance or repair, whereas jointed bridges suffered major damage from de-icing chemicals and pavement pressure. Consequently, more bridge engineers began to appreciate the merits of integral bridges for short- or moderate-length bridges. Gradually, design changes were made and longer integral bridges were built and evaluated. In 1946, Ohio’s initial length limitation for its continuous concrete slab bridge was 175 ft. (53.3 m). In a 1973 study of integral construction [4], four states reported that they were using integral steel bridges and 15 states were using integral concrete bridges in the 201–300 ft. (61–90.4 m) range. In a 1982 study, even longer bridges were reported. Continuous integral bridges with steel main members have performed successfully for years in the 300-ft. [91.4-m] range in such states as North Dakota, South Dakota
8
Integral and Semi-integral Bridges
and Tennessee. Continuous integral bridges with concrete main members, 500 to 800 ft. (152.4 to 243.8 m) long have been constructed in Kansas, California, Colorado, and Tennessee. [5]
As of 1987, 11 states reported building continuous integral bridges in the 300 ft. (91.4 m) range. Missouri and Tennessee reported even longer lengths. Missouri reported steel and concrete bridges in lengths of 500 and 600 ft. (152.4 and 182.9 m), respectively. Tennessee reported lengths of 400 and 800 ft. (121.9 and 243.8 m) for similar bridges. Actually, 20 of 30 transportation departments, or 60 percent of those departments responding to the 1987 survey, were using integral construction for continuous bridges. The attributes of integral bridges have not been achieved without some concerns about high unit stresses. Parts of these bridges operate at very high stresses levels, levels that cannot easily be quantified. These stresses are significantly above those permitted by current design specifications. In this respect, bridge engineers have become rather pragmatic. They would rather build cheaper integral bridges and tolerate these higher stresses than build the more expensive jointed bridges with their lower stresses and concomitant vulnerability to destructive pressures and deicing-chemical deterioration. This attitude was expressed by Clelland Loveall, then Engineering Director for the Tennessee DOT. At the time he wrote: In Tennessee DOT, a structural engineer can measure his ability by seeing how long a bridge he can design without inserting an expansion joint. … Nearly all our newer (last twenty years) highway bridges up to several hundred ft. have been designed with no joints, even at abutments. If the structure is exceptionally long, we include joints at the abutments but only there. … Joints and bearings are costly to buy and install. Eventually, they are likely to allow water and salt to leak down onto the superstructure and pier caps below. Many of our most costly maintenance problems originated with leaky joints. So we go to great lengths to minimize them. [6]
Tennessee DOT is still leading the bridge engineering profession in the construction of longer and longer integral bridges. Under their present Engineering Director, Edward Wasserman, Tennessee DOT recently completed the Happy Hollow Creek Bridge, a seven-span prestressed concrete curved integral bridge with a total length of over 1,175 ft. (358 m) (see the photograph at start of this chapter). As shown in this photograph, tall flexible twin circular column piers support the superstructure of this outstanding structure. A single row of steel H-piles is used to support each abutment. Although, to some engineers, the length of this structure may seem extreme, it is well within Tennessee DOT’s Bridge Design Policy Statement regarding the length of integral bridges. With respect to expansion joint selection, the policy statement stipulates: When the total anticipated movement at an abutment is less than two (2) inches [50 mm] and the abutment is not restrained against movement, no joint will be required and the superstructure and abutment beam will be constructed integrally. [7]
In 1997, six bridge engineers from the United Kingdom participated in a study tour of integral bridges in North America. This task group visited Ohio, Tennessee,
Chapter 1
Integral Bridges
9
Missouri, Washington State, California, and Ontario. They also visited Construction Technology Laboratories of Skokie, Illinois, where comprehensive integral bridge research was under way. In their report of the study tour, they generalized their opinions about the performance of integral bridges inspected by the task group as follows: Integral bridges were inspected in five States in the USA, and in Ontario, Canada. In all cases these were found to be performing well. It is important to note that, in contrast, the non-integral bridges that were seen all had leaking expansion joints, and several were deteriorating badly. The few minor problems in integral bridges that were found were all considered to be due to poor detailing. Integral construction transfers possible problems from the abutment to the approach slab and pavement. No integral bridges were seen on the tour where the integral concept was considered to have been inappropriate. [8]
Although bridge engineers have conditioned themselves to tolerate higher stress levels in integral bridges, occasionally their design control is not sufficient to prevent these high stresses from resulting in relatively minor structural distress. In this respect, consider some of the responses to survey questions about noticeable structure distress.
Structural distress Responses to an early survey about continuous integral bridges indicated a rather widespread concern by bridge engineers for the potentially high stresses that would be present in longer integral bridges [4]. This concern, more than any other, appeared to be responsible for the early lack of enthusiasm for using integral construction for the longer continuous bridges. Although most integral bridges perform adequately, many of them operate at high stress levels. For instance, an abutment supported on a single row of piles is considered flexible enough to accommodate thermal cycling of the superstructure and the dynamic end rotations induced by the movement of vehicular traffic. Nevertheless, the steel piles of such an abutment are routinely subjected to axial and flexural stresses approaching, equaling, or exceeding yield stresses [5, 9]. Occasionally, a combination of circumstances results in visible distress. Responding to a 1973 survey, a number of bridge engineers said that some integral bridge abutment wingwalls had minor cracks [4]. This problem was corrected by the use of more generous wingwall reinforcement. Other engineers reported pile cap cracking, cracking that appears to have been eliminated by providing more substantial pile cap connection reinforcement and by rotating steel H-piles to place the weak axis normal to the direction of bridge movement. In a 1984 article in Concrete International, Gamble [10] emphasizes the importance of considering restraint stresses in cast-in-place construction. He discusses cracking that occurred in a continuous concrete frame bridge with footings that were founded in bedrock. Even though the concrete of this structure was considerably below the specified cylinder strength, and shear reinforcement did not meet current requirements, failure of the structure was attributed to its stiffness and
10
Integral and Semi-integral Bridges
resistance to shrinkage and contraction of its bridge deck. Failures of this type emphasize the necessity of achieving suitable flexibility in supporting substructures and conservative reinforcement to withstand the secondary stresses induced by foundation restraint and superstructure shortening. Currently, precast prestressed concrete and prefabricated steel superstructures are generally replacing small cast-in-place bridges in many states and provinces. Consequently, problems associated with initial shrinkage of superstructures are gradually being eliminated. However, where cast-in-place construction continues to be used for substructures, flexibility remains a critical part of bridge design. In this respect, Loveall of Tennessee DOT provides an example of the lack of flexibility in substructure design: Structural analysis of our no joint bridges indicates that we should have encountered problems, but we almost never have. Once we tied the stub of an abutment into rock, and the structure cracked near its end, but we were able to repair the bridge and install [a] joint while the bridge was under traffic. The public never knew about it. That was one of few problems. [6]
Development of new forms of construction will be accompanied by instances of structural distress, and this has certainly been true with continuous integral bridges. However, as indicated by the 1987 mail survey, the application of integral bridges increased exponentially from its beginnings in the 1930s and was beginning to taper off in the 1980s when 20 of 30, or 60 percent, of responding transportation departments were using integral bridge construction in one form or another for longer and longer bridges. Presumably, with continued care and consideration, it appears that the use of integral bridges will continue to see a gradual increase in the numbers of transportation departments adopting the integral bridge concept for routine bridge applications.
Integral bridge details Abutment details of integral bridges used by six transportation departments, as of 1989, when the text that serves as the basis of this chapter was originally prepared, are presented in Figures 1.4 and 1.5. Presumably, the details presently used by these same departments have remained essentially the same except for minor changes in dimensions and reinforcement. What has changed in the intervening years are the numbers of other departments that have adopted standard integral details for their routine bridges. It is probably not an accident that a fair amount of similarity is evident in these designs because structural details from early successful designs are adapted and improved by other bridge engineers for use by their departments. Even though there are similarities, there are also differences that reflect the various types of bridges being built, and the care and concern being given to the conception and development of specific details. It should also be realized that these sketches are mere “bare bones” presentations. They do not reflect other important design aspects and construction procedures that should be considered in the application of these details for specific applications. All of these aspects could not be illustrated and properly described in a chapter as brief as this one. Nevertheless, because these
Chapter 1
(a)
Integral Bridges
11
(b)
(c)
Figure 1.4 Integral abutment: (a) Iowa DOT; (b) Pennsylvania DOT; and (c) North Dakota DOT.
aspects can have a considerable effect on the performance, integrity, and durability of integral designs, it is appropriate to mention something about some of them, especially passive pressure and pile stresses, for those engineers who will be considering such designs for the very first time. Passive pressure To minimize passive pressure development in structure backfill by an elongating integral bridge, bridge design engineers have used a number of controls, devices and procedures. Including but not limited to the following practices, they have:
• • • • •
limited bridge length limited bridge skew limited abutment type to embankment supported stubs provided embankment benches to minimize the length of transverse wingwalls limited the vertical penetration of abutments into the benches
12
Integral and Semi-integral Bridges
(a)
(b)
(c)
Figure 1.5 DOT.
• • • • • •
Integral abutment: (a) Illinois DOT; (b) Tennessee DOT; and (c) Ohio
limited the clearance between the superstructure and embankment benches to make the abutment surfaces exposed to passive pressure as small as possible provided well-drained select granular backfill at abutments provided turn-back wingwalls to minimize total longitudinal pressure on the abutments provided approach slabs to prevent live load surcharging of backfill, and to minimize vehicular compaction of backfill. provided approach slabs with curbs adjacent to curbed bridges to protect backfill from erosion used a semi-integral abutment design to eliminate passive pressure below the bridge seat and permit the use of a semi-rigid foundation design (Figure 1.6).
Chapter 1
Figure 1.6
Integral Bridges
13
Ohio DOT’s first semi-integral abutment (1979).
Pile stresses Knowing that longitudinal forces on superstructures are somewhat directly related to the resistance of abutment pile foundations to longitudinal movement, design engineers have:
• • • • • • • •
provided each abutment foundation with a single row of slender vertical piles provided only those pile types that could tolerate a considerable amount of distortion without failure; in this respect, it has shown that steel H-piles are the most suitable pile type for longer integral bridge applications [11] oriented the weak axis of H-piles normal to the direction of pile flexure provided prebored holes filled with granular material provided an abutment hinge (see Figure 1.5c) to minimize pile flexure limited the length of the structure to minimize pile flexure limited structure skew angle provided semi-integral abutments to minimize restraint on superstructures due to longitudinal movement.
Questionnaires A number of questionnaires about integral bridge practices have been circulated in recent years. The responses reflect the policies, attitudes, and opinions of those engineers responsible for bridge design policies. They also show how some of these attitudes and opinions have changed during the last couple of decades. In 1973, Emanual et al. [4] received responses about the then current design practices from
14
Integral and Semi-integral Bridges
43 transportation departments. In 1982, Wolde-Tinsae et al. [5] used a questionnaire as part of an investigation into non-linear pile behavior. They tabulated the responses that they received from 29 transportation departments. Greimann et al. [12] elicited responses from 30 transportation departments on their pile orientation practices for skewed integral bridges. In 1987, Wolde-Tinsae and Klinger [13] solicited responses from selected transportation departments in the United States, Canada, Australia, and New Zealand. (The reports by Wolde-Tinsae et al. [5], Greimann et al. [12], and Wolde-Tinsae and Klinger [13] also contain valuable bibliographies for those interested in a more in-depth study of available research on the behavior of integral bridges and the performance of abutment pilings.) In addition, 1n 1988, the author received responses from 30 transportation departments describing the limitations that these departments used to control the behavior and performance of the integral bridges designed and constructed by them [2]. Integral conversions Following the trend toward the use of end-jointed continuous construction and the use of jointless continuous construction, transportation departments are also beginning to convert existing multiple-span bridges from simple to continuous spans. This effort began with Wisconsin and Massachusetts DOTs in the 1960s and has gathered strength in the last several decades. Currently, more than 30 percent of the transportation departments have converted one or more bridges from multiple simple spans to continuous spans. Although the 1988 mail survey suggested considerable activity, it was not indicative of the number of bridges that had been converted. For example, positive responses were received from only two departments to the following question: “In recent years, have you converted any bridges from multiple simple spans to continuous spans to eliminate deck joints?” The Ontario Ministry of Transportation and Communications responded: We are modifying a few structures from simple spans to continuous spans, eliminating deck joints in the process. …[2, p. 27]
The Texas Department of Public Transportation (DPT) responded: In recent years, we have eliminated numerous intermediate joints. Generally, this is done while replacing the slab. We simply place the slab continuous across the beams. On a few occasions, we have removed only the joint and surrounding deck area, added reinforcement, and replaced that portion of the deck thus tying the adjacent spans together. [2, p. 27]
Tennessee DOT also has been actively converting simple-span bridges. In a paper on jointless bridges, Edward Wasserman, Engineering Director of Structures, described and illustrated a number of such conversions [14]. To give this movement some direction, in 1980, the Federal Highway Administration (FHWA) issued a technical advisory on the subject [15]. That advisory in part recommends that a study of the bridge layout and existing movable deck joints be made “to determine which joints can be eliminated and what modifications are necessary to
Chapter 1
Integral Bridges
15
revamp those that remain to provide an adequate functional system. …” Further, it recommends: For unrestrained abutments, a fixed integral condition can be developed full length of shorter bridges. An unrestrained abutment is assumed to be one that is free to rotate, such as a stub abutment on one row of piles or an abutment hinged at the footing. … [W]here feasible, develop continuity in the deck slab. Remove concrete as necessary to eliminate existing armoring, and add negative moment steel at the level of existing top-deck steel sufficient to resist transverse cracking. [15]
The detail in Figure 1.7a from the FHWA Technical Advisory mirrors the details used by the Texas Department of Public Transportation (Texas DPT) for its conversion of multiple simple spans to continuous spans. Note that Figure 1.7a shows that only the slab portion of the deck is made continuous. The simply supported beams remain simply supported. For such construction, it is important to ensure that one or both of adjacent bearings supporting the beams at a joint are capable of allowing
(a)
(c)
(b)
(d)
Figure 1.7 (a) Integral conversion at piers, Texas DPT (copied from the FHWA Technical Advisory [15]); (b) integral conversion of existing beams at piers, Utah DOT; (c) integral conversion of precast I-beams at piers during original construction, Wisconsin DOT; and (d) integral conversion of prestressed box beams at piers during original construction, Ohio DOT.
16
Integral and Semi-integral Bridges
horizontal movement. Providing for such movement will prevent large horizontal forces from being imposed on bearings due to rotation of adjacent spans and continuity of the deck slab. Utah DOT has also converted some simple span bridges to continuous spans by using a design similar to the one illustrated in Figure 1.7b. For deck slabs with a bituminous overlay, an elastomeric type of membrane can be used under the overlay to waterproof the new slab section over the piers. With a design like this, it is understood that the deck slab would be exposed to longitudinal flexure due to the rotation of beam ends responding to the movement of vehicular traffic. However, for shortand medium-span bridges, the deck cracking associated with such behavior is preferred by some over the long-term adverse consequences associated with open movable deck joints or a poorly executed joint seals. In new construction, the conversion of simple spans to continuous spans is rather commonplace. Figure 1.7c shows the detail used by Wisconsin DOT for the construction of prestressed concrete I-beam bridges. A substantial concrete diaphragm is provided at piers between the ends of the simply supported beams of adjacent spans. The diaphragm extends transversely for the width of the superstructure. Then a continuous reinforced concrete deck slab is placed to integrate the beams, diaphragms, and slab, thereby providing a fully composite continuous superstructure. This type of prestressed concrete I-beam construction now appears to be standard for many transportation departments. Figure 1.7d illustrates the standard detail used by Ohio DOT to achieve continuous bridges by using simply supported, prestressed concrete box beams with continuity connections at the piers. Boxes are placed side by side and then transversely bolted together. Finally, continuity reinforcement is placed and reinforced concrete closure placements are made. In a 1969 paper, Freyermuth [16] gives a rather complete description of the analysis procedures that can be used to achieve continuity in a bridge composed of a continuously reinforced concrete deck slab on simply supported, precast, prestressed beams. Conversion of existing bridges, by replacing either the deck completely or only portions of the deck adjacent to movable deck joints at piers, can be accomplished by following the procedures developed by Freyermuth for new structures. Obviously, for existing bridges, creep effects will be negligible. Shrinkage effects for other than complete deck slab replacements should also be negligible. Not only does such continuous conversion eliminate troublesome joints, but the continuity achieved also results in a slightly higher bridge load capacity because positive moments due to live load are reduced by continuous rather than simple span behavior. Although too recent to consider in terms of a design trend, conversion of nonintegral abutments to achieve integral bridges or semi-integral bridges for both single- and multiple-span continuous bridges has begun. Figures 1.8–1.10 illustrate design details used for a number of conversions by Ohio DOT. Reconstruction of these abutments was made necessary by the substantial damage caused by pavement growth and pressure, by de-icing chemical deterioration, or both. Instead of replacing backwalls and joints, and in some cases bearings and bridge seats as well, it was decided to pattern reconstruction after the design details used by the department for its new integral and semi-integral bridges. In this way subsequent concern about
Chapter 1
(a)
Integral Bridges
17
(b)
Figure 1.8 Conversion of a very short continuous bridge with movable deck joints at the superstructure/abutment interface (a), into a continuous bridge with integral abutments (b), Ohio DOT.
(a)
(b)
Figure 1.9 Conversion of a continuous bridge with movable deck joints at the superstructure/abutment interface (a), to a continuous bridge with integral abutments (b), Ohio DOT.
the adverse effects of pavement pressure and de-icing chemical deterioration were minimized. When considering the design trends toward integral types of construction, it should not be surprising to learn that a number of transportation departments have also begun to retrofit steel beam and girder bridges constructed with intermediate movable deck joints with hinges into fully continuous structures. Conversion of
18
Integral and Semi-integral Bridges
(a)
(b)
Figure 1.10 Conversion of single- or multiple-span continuous bridges with movable deck joints at the superstructure/wall-type abutment interface (a), into single- or multiple-span continuous semi-integral bridges (b), Ohio DOT.
(a)
(b)
Figure 1.11 Conversion of multiple-span continuous bridges with intermediate deck joints and hinges (a), into continuous bridges with bolted splices (b), Ohio DOT.
these structures is being accomplished by replacing the hinges and leaking joints with bolted splices and continuous deck slabs (Figure 1.11). These joints and hinges were originally intended to accommodate long-term abutment settlement. But as these structures are now more than 20–30 years old, and as embankments are now essentially fully consolidated, the need for these movement systems no longer exists. However, where such labor-intensive conversions are not fully cost-effective, some
Chapter 1
Integral Bridges
19
of these jointed superstructures are being completely replaced with fully continuous superstructures with integral abutments. Finally, within the last two decades, Ohio DOT has converted many of its continuous bridges with movable deck joints at the superstructure/abutment interface by completely replacing independent semi-rigid stub abutments (see Figure 1.8a) with integrated flexible stub abutments (see Chapter 7, Figure 7.7). Presumably, this same rehabilitation technique is now being used by many other transportation departments throughout the United States. However, the number of such retrofitted structures is probably greater in Ohio because most of Ohio’s old multiple-span bridges were originally constructed as continuous bridges. In fact, one would be hard pressed to find a multiple-span bridge in Ohio that was not of continuous construction. These are the bridges that are now being converted in record numbers to fully integrated construction.
Summary As the trends noted above continue, it appears that the use of continuous construction for multiple-span bridges will become standard for all transportation departments in the very near future. It also appears that the use of integral abutments for single- and multiple-span continuous bridges will increase when comprehensive and conservative guidelines for their use become more readily available, and when their long-term performance has been more fully documented. Presumably, the next decade or two will see a burgeoning in the retrofitting of simply supported multiple-span bridges to continuous bridges and from non-integral to integral bridges. When more information on the operating stress levels for these structures is developed and when more fully described design details and construction procedures for integral conversions become available, bridge engineers will be able to more fully justify their consideration. Until then, much intuition and prudent judgment will continue to be used to ensure that integral construction and conversion techniques will provide the structure service life needed to justify their adoption and continued use.
Epilogue As a preliminary to the 2005 FHWA Conference on Integral Abutments and Jointless Bridges, a nation-wide survey was conducted of all major transportation departments of the United States. This survey posed various questions regarding the use of integral and semi-integral bridges. With respect to the number of these structures that have been employed, the following summary statement was made: The survey responses indicate an increase in the number of integral [bridges] of over 200% in the last ten years. As in 1995, Tennessee continues to have over 2000 integral … bridges, but Missouri reports having 4000 integral … bridges, which represents the largest amount of integral bridges. An increase in the number of integral [bridges], since 1995, is most evident in the northern states where Illinois, Kansas and Washington all reported having
20
Integral and Semi-integral Bridges
over 1000 in service. In addition, Michigan, Minnesota, New Hampshire, North Dakota, South Dakota, Oregon, Wyoming and Wisconsin, reported having between 100–500 integral bridges in service. Unlike the northern states, the southern states like Florida, Alabama and Texas do not use integral [bridges] and reported having one or [no] integral [bridges]. [17]
References 1. Cross, H., “Analysis of Continuous Frames by Distributing Fixed End Moments,” ASCE Proceedings, American Society of Civil Engineers, New York, May 1930. 2. Burke, M. P. Jr., National Cooperative Highway Research Program Synthesis 141: Bridge Deck Joints, Transportation Research Board of the National Academies, Washington, D.C., 1989. 3. Burke, M. P. Jr., “Bridge Approach Pavements, Integral Bridges and Cycle-Control Joints,” Transportation Research Record No. 1113, Transportation Research Board of the National Academies, Washington, D.C., 1987. 4. Emanual, J. L., et al., “Current Design Practice for Bridge Superstructures Connected to Flexible Substructures, University of Missouri-Rolla, Rolla, Missouri, 1973. 5. Wolde-Tinsea, A. M., Greimann, L. F., Yang, P. S., Nonlinear Pile Behavior in Integral Abutment Bridges, Iowa State University, Ames, Iowa, 1982. 6. Loveall, C. L., “Jointless Decks,” Civil Engineering, American Society of Civil Engineers, New York, 1985, pp. 64–67. 7. “Expansion Joint Selection,” Tennessee Structures Memorandum, MO 045, Tennessee Department of Transportation, Nashville, Tennessee, 1989. 8. Nicholson, B. A., et al., Integral Bridges: Report of a Study Tour of North America, Concrete Bridge Development Group, Century House, Telford Avenue, Crowthorn, Berkshire, United Kingdom, 1997, pp. 93. 9. Jorgenson, J. L. “Behavior of Abutment Piles in an Integral Abutment Bridge,” Transportation Research Record No. 903, Transportation Research Board of the National Academies, Washington, D.C., 1983. 10. Gamble, W. L., “Bridge Evaluation Yields Valuable Lesson,” Concrete International, American Concrete Institute, Farmington Hills, Michigan, 1984, pp. 68–74. 11. Oesterly, R. G., “Flexible Pile Tests,” Construction Technologies Laboratory, Skokie, Illinois. (unpublished report). 12. Greimann, L. F., Wolde-Tinsea, A. M., Yang, P. S., “Skewed Bridges with Integral Abutments,” Transportation Research Record No. 903, Transportation Research Board of the National Academies, Washington, D.C., 1983. 13. Wolde-Tinsae, D. M., Klinger, J. E., “Integral Abutment Bridge Design and Construction,” Report FHWA/MD-87/04, Maryland Department of Transportation, Annapolis, Maryland, 1987. 14. Wasserman, E., “Jointless Bridges,” Engineering Journal, American Society of Civil Engineers, New York, Vol. 24, No. 3, 1987. 15. FHWA, “Bridge Deck Joint Rehabilitation (Retrofit),” Technical Advisory T1540.16 Federal Highway Administration, Washington, D.C., 1980. 16. Freyermuth, C. L., “Design of Continuous Highway Bridges with Precast Prestressed Concrete Girders,” ACI Journal, American Concrete Institute Farmington Hills, Michigan, Vol. 14, No. 2, 1969. 17. Maruri, R. F., Petro, S. H., “Integral Abutments and Jointless Bridges (IAJB) 2004 Survey Summary,” Presentations and Proceedings, Integral Abutments and Jointless Bridges, 2005, Federal Highway Administration, Baltimore, Maryland, 2005.
Chapter 2
Bridge Damage and the Pavement G/P Phenomenon
If the world has nearly destroyed itself, it is not from lack of knowledge … but is due to the fact that the mass of men have not applied to public policy knowledge they already possess, which is indeed of almost universal possession, deducible from the facts of everyday life. If this is true – and it seems inescapable – then no education which consists mainly in the dissemination of “knowledge” can save us. If men can disregard in their policies the facts they already know, they can just as easily disregard new facts which they do not at present know. What is needed is the development in men of that particular type of skill which will enable them to make social use of knowledge already in their possession; enable them to apply simple, sometimes self-evident truths to the guidance of their common life. Sir Norman Angell
Introduction Innumerable bridges both in the United States and abroad have been and continue to be damaged by the restrained growth of jointed rigid pavement. As a result of such damage, it appears that the pavement growth/pressure (G/P) phenomenon responsible for this damage is not fully appreciated by many pavement research 21
22
Integral and Semi-integral Bridges
specialists, and it appears to be unknown to or not fully appreciated by many pavement and bridge maintenance engineers. This phenomenon is not now described in bridge engineering textbooks, nor is it identified in the American Association of State Highway and Transportation Officials’ (AASHTO’s) Standard Specifications for Highway Bridges [1]. In addition to this apparent somewhat mysterious lack of recognition, it also appears that many bridge design engineers are unaware of the pavement G/P phenomenon. This presumption is based on the fact that these engineers continue to design and construct bridges with movable deck joints in conjunction with jointed concrete pavements. These are the bridges that are vulnerable to pavement growth/pressure-induced damage. In this respect, it also appears that these bridge design engineers are either unfamiliar with or continue to ignore the significant attributes of integral and semi-integral bridges (see Appendix 2), bridges that are highly resistant to such damage. Based on some recent statements and recommendations in national pavement research reports, and in published papers of some state pavement maintenance engineers, it also appears obvious that either the pavement G/P phenomenon is neglected entirely by many pavement engineers, or its significance with respect to the long-term (i.e., ≥10 years) function and durability of both pavements and bridges is not fully understood. As a result, a few misguided pavement design and maintenance practices have recently been advocated and adopted by some state transportation departments, practices that will have a significantly adverse effect on the long-term integrity and durability of both their pavements and their abutting bridges. Concern that such ill-conceived pavement design and maintenance practices might achieve widespread popularity (due primarily to their enticing lower first costs and lower periodic maintenance costs, regardless of the significantly greater long-term pavement and bridge rehabilitation costs) has motivated this author to assemble factual documentation and illustrations and prepare this elaboration of the pavement G/P phenomenon and its destructive potential. As bridge and pavement engineering expertise and practices will continue to change (hopefully for the better), the documentation, illustrations, explanations, and discussion presented herein should, in the author’s opinion, provide a positive direction for those changes. Such changes should help encourage a greater awareness by both pavement and bridge engineers of the pavement G/P phenomenon and its destructive potential, encourage long-term research on this phenomenon, motivate engineers to use more effective pavement and bridge design and maintenance practices, and ultimately help them to achieve more cost-effective, safer, and more durable bridges. The first part of this chapter describes the damaging effect of the pavement G/P phenomenon (see Appendix 2) on three different large bridges containing movable deck joints at both the superstructure/abutment interface and intermediate locations throughout the superstructure. It also provides a brief explanation of the G/P phenomenon. The second part of the chapter describes the effects of this phenomenon on end-jointed continuous bridges and on integral bridges. It also describes the troubling lack of published documentation about this phenomenon and its destructive potential. For those who desire a more complete explanation of this phenomenon, Appendix 1 has been included in this book expressly for that purpose.
Chapter 2 Damage and the Pavement G/P Phenomenon
23
Three bridges Three radically different bridge types – separated by both time and distance – shared a similar fate because each is a multiple-span bridge with movable deck joints at the superstructure/abutment interface, and at intermediate locations throughout the superstructure. In addition, these bridges were built in conjunction with jointed concrete approach pavements. The behavior of these three bridges can be considered somewhat characteristic of many similar smaller bridges located throughout the United States. The three bridges are: the Old Third Street Viaduct of Cincinnati, Ohio; the John F. Kennedy Memorial Bridge of Louisville, Kentucky and Jeffersonville, Indiana; and the Pecos River Bridge of Carlsbad, New Mexico. Old Third Street Viaduct This viaduct consisted of an ugly hodge-podge of structure types, typically continuous steel girders supported by two-legged steel frames (Figure 2.1). But at the shallow western end of the structure, each pier consisted of two short rectangular reinforced concrete columns. In the summer of 1970, after just 11 years of service, bridge maintenance engineers discovered long, essentially vertical cracks in the two columns of Pier 1 (Figure 2.2). The two columns of that pier provided part of the vertical support for the first two continuous spans, and their fixed bolster bearings provided complete longitudinal support for the first of numerous superstructure segments. As the design of these pier columns and their concrete quality were judged to be adequate for the loads to be supported, and because maintenance engineers were confident that pier reinforcement had been provided in accordance with plan
Figure 2.1
Old Third Street Viaduct, Cincinnati, Ohio, 1959–2001.
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Integral and Semi-integral Bridges
Figure 2.2 Pier 1 of the Old Third Street Viaduct. The vertical cracks in this pier column were induced by the pavement growth/pressure (G/P) phenomenon.
requirements, the integrity of the pier was restored by injecting the cracks with an epoxy adhesive. Periodic inspections of these pier columns made throughout the rest of the year revealed no new or extended cracks, suggesting that the epoxy repair had been successful. During the following summer, however, new and similar cracks began to appear. So instead of further epoxy injections, maintenance personnel responded by apply-
Chapter 2 Damage and the Pavement G/P Phenomenon
25
ing the external hardware visible in Figure 2.2. Subsequently, a broader examination of the structure was made to determine the cause(s) of these unusual cracks so that a more suitable maintenance response could be made. Clues to the cause of pier cracking were revealed when the condition of the adjacent wall-type abutment was considered. For example, the movable deck joint at the west abutment was tightly closed, indicating a permanent 2 in. (50 mm) longitudinal movement from the as-constructed position; the abutment breastwall was tilted toward the superstructure; there were large, essentially vertical cracks between the breastwall and turn-back wingwalls; the approach roadway consisted of jointed concrete pavement; and pier cracking reappearance did not take place until warm summer temperatures were reached. Although there was no visible evidence of pavement or abutment backwall distress, and the approach pavement was only 11 years old, it nevertheless appeared highly likely that the pavement G/P phenomenon was responsible for moving and tilting the west abutment and cracking the first fixed pier of this bridge. More specifically, it appeared that the growing approach pavement jammed the west abutment toward the bridge superstructure, thereby moving and tilting the abutment and closing the movable deck joint at the superstructure/abutment interface. Continual growth of the pavement subsequently moved both the abutment and the first superstructure segment toward the second segment, thereby commencing closure of the movable deck joint between the first and second segments. But the fixed bearings and the two short stiff columns of Pier 1 resisted longitudinal movement of the first superstructure segment. As the forces that can be generated by the pavement G/P phenomenon are so huge, and as they are somewhat proportional to the degree of restraint against pavement growth provided by the bridge, the cracking of the Pier 1 columns was only the first indication of greater forces and more extensive future pier and abutment fracturing, unless pavement pressure relief joints were installed in the bridge approaches. As a first attempt at pressure relief, the western approach pavement was cut transversely so that a 4 in. (102 mm) plank of compressible polyethylene filler could be installed, filler that was manufactured specifically for pavement pressure relief purposes. This installation was made in March 1972. Immediately following the cutting of pavement and the release of longitudinal pavement forces, the wall-type abutment tilted backward ⅝ in. (16 mm) toward the bridge approach, and the slightly tilted Pier 1 columns rotated back to vertical. These responses provided clear visual evidence that the uncut and growing pavement was responsible for the closed movable deck joints and damage to the structure. In March of 1973, just 1 year after its installation, the original 4 in. (102 mm) wide polyethylene pressure relief joint filler was measured and found to be only 2.5 in. (64 mm) wide. This filler thickness change indicated pavement growth and compression of the polyethylene filler of 1.5 in. (38 mm) in just one-year’s time. John F. Kennedy Memorial Bridge Similar trouble for the second of these bridges, the John F. Kennedy Memorial Bridge (Figure 2.3), was brought to the public’s attention when a local newspaper questioned “What’s wrong with the Kennedy Memorial Bridge?” [2]. This bridge consists of continuous through-truss main spans and continuous deck-type steel
26
Integral and Semi-integral Bridges
Figure 2.3 John F. Kennedy Memorial Bridge, Louisville, Kentucky and Jeffersonville, Indiana, 1963.
girder approach spans, stub-type embankment supported abutments, and cap-andround column piers. As described for the Old Third Street Viaduct, the movable deck joints at both ends of the northernmost deck-type superstructure segment were closed, the supporting fixed pier was tilted 5 in. (127 mm) to the south, and the northernmost rocker bearings at the other piers were tilted in the same direction (Figure 2.4). The north abutment had also been moved southward, probably about 7 in. (178 mm) (2 in. [51 mm] joint closure plus 5 in. [127 mm] pier movement). Similar to the Old Third Street Viaduct, the pavement G/P phenomenon was probably responsible for this movement. In 1991, Indiana officials reported that: The northern approach to the bridge has been tilting southward for 8 to 10 years, according to old inspection photographs. The leaning was never enough to cause alarm. [2]
This bridge and its approach pavements were built in 1964. It appears that the approach pavements were about 27 years of age when the growth of pavements had progressed far enough to have closed the movable deck joints and moved all of the northern approach bridge elements (abutment, superstructure, and pier) enough to have provoked public concern about the structure’s stability. Apparently, the fixed pier columns (and presumably their pile-supported foundations) were tall and flexible enough to have tolerated 5 in. (127 mm) of longitudinal superstructure movement and pier tilting without noticeable pier distress. In response to this magnitude of movement, the concrete approach pavements were cut and pressure relief joints installed to eliminate restraint against pavement
Chapter 2 Damage and the Pavement G/P Phenomenon
27
Figure 2.4 A newspaper illustration that appeared in the October 24, 1991, edition of the Louisville Courier Journal showing the condition of the Northernmost approach spans of the John F. Kennedy Memorial Bridge. The illustration was slightly modified by the author to indicate closed deck joints and more representative abutment details.
growth and to minimize pressure transmission from the pavement to the bridge. As embankment and subsoil consolidation and translation at the north approach may have also contributed somewhat to substructure movement, motion detectors were implanted in the north abutment embankment. These detectors were used to monitor possible embankment movements and to ensure that the installation of pavement pressure relief joints was a sufficient response to prevent further longitudinal movement of both superstructure and substructure elements. Subsequent monitoring of the detectors indicated that the embankment was stable and not contributing to substructure movement. Presumably, the pressure relief joints will continue to be monitored and replaced or widened to ensure against further damage from the pavement G/P phenomenon. The movable deck joints have been rebuilt to facilitate anticipated superstructure movements due to live load rotations and longitudinal thermal movements. The rocker bearings will probably be righted when other maintenance repairs make such an effort more cost-effective. Pecos River Bridge Similar trouble for the Pecos River Bridge of Carlsbad, New Mexico (Figure 2.5) came to a head when local maintenance personnel were no longer able to contend with this structure’s unusual behavior and progressive deterioration. This bridge
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Integral and Semi-integral Bridges
Figure 2.5
Pecos River Bridge, Carlsbad, New Mexico, 1941.
consists of eight deck-type, simply supported, rolled-beam spans with reinforcedconcrete wall-type piers and abutments. An inspection of the structure in 1991 revealed that the three easternmost movable deck joints were closed. The top of the massive wall-type east abutment had been moved and tilted to the west about 5.5 in. (140 mm), the ends of the deck slabs were crushed, and rocker and bolster bearings were shifted and tilted so much that they were edge bearing on the bridge seats (Figure 2.6). Bridge seats of the substructure units supporting the easternmost spans were badly cracked and fractured as well. As a result of the magnitude of the movement at the east abutment, it would appear likely that the adjacent piers were tilted to the west as well. The complete history of the bridge and its concrete approach pavements is uncertain. The bridge was constructed in 1941, but the date of construction of the present approach pavement has not been determined. A report about the bridge stated that, in 1983, the deck was repaired and overlaid, some repair work was done on the substructure, and bridge bearings and structural steel were repainted. Although the precise age of the approach pavement had not been determined, it was apparently old enough for its growth to have been responsible for the bridge’s recent rapid deterioration. From an unpublished inspection report about this bridge, state bridge engineers concluded: “We believe that the [abutment tilting,] deck crushing and bearing misalignments have been caused by the pavement shoving against the [abutment] backwall and bridge deck at the east end…. We have noticed similar problems with pavement shoving at many other bridges. However, the amount of movement and subsequent damage to Bridge No. 1838 is the worst
Chapter 2 Damage and the Pavement G/P Phenomenon
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Figure 2.6 Rocker and bolster bearings at Pier 7 of the Pecos River Bridge. The rocked bearings of the eighth span were tilted and bearing against the bolster bearings of the seventh span. Bolster-bearing anchors bars were bent and the bearings themselves were horizontally displaced. Not visible are major fractures in pier walls below the bridge seat.
we have seen.” In addition to recommending various structure repairs, the immediate installation of pavement pressure relief joints in the bridge approaches was recommended.
Pavement G/P phenomenon As described above, serious trouble for the Old Third Street Viaduct, the John F. Kennedy Memorial Bridge, and the Pecos River Bridge became evident after these structures and their approach pavements were 11, 27, and less than 30 years old, respectively. As this trouble has been identified with the long-term behavior of jointed concrete approach pavement, it is obviously important that bridge design engineers become familiar with the long-term behavior of such pavements. They also need to understand the causes and consequences of the pavement G/P phenomenon, the phenomenon responsible for such an adverse effect on the performance, integrity, and durability of highway bridges. For this purpose, Appendix 1 has been appended to this book to aid bridge design engineers gain suitable familiarity with this phenomenon. In addition, a brief description of the phenomenon is provided below to introduce the subject to those who are becoming aware of it for the first time. If design had to contend with only the response of structures (pavement and bridges) to ambient temperature ranges, achievement of an efficient and functional
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transportation system would be relatively easy. However, concrete shrinkage and the less-than-ideal effect of traffic maintenance practices have compounded the problems faced by pavement and bridge maintenance engineers. Pavement contraction joints When pavement segments between transverse contraction joints contract longitudinally in response to lowering temperature and moisture levels, the transverse contraction joints between these segments open wider. Conversely, these joints become narrower due to the segments’ response to rising temperature and moisture levels. However, after the contraction joints open and remain open at low temperatures and moisture levels, compression-resistant fine roadway debris infiltrates the cracks below the saw-cut surfaces of the joints. This infiltration prevents subsequent complete closure to an as-constructed condition. Joint opening, infiltration of debris, and partial closing continue in sequence with daily and yearly temperature and moisture cycles. Of course, debris infiltration is facilitated where de-icing chemicals are used to ensure dry pavements (and consequently, open contraction joints) during low winter temperatures. Infiltration of these joints by compressive-resistant debris begins almost as soon as the cracks form below the saw-cut surfaces. Unsealed joints are infiltrated from the top, sides, and bottom. For “sealed” joints (actually a misnomer because only the upper surfaces of such joints are initially sealed), infiltration begins at the open sides and bottoms. The movement of surface water that penetrates pavement and shoulder joints from above, and ground water that seeps through shoulders and migrates along the sub-base below the joints, facilitate this infiltration. As contraction joint seals begin to fail because of a combination of age degradation, low temperature stiffening, traffic abrasion, neglect, etc., debris infiltration accelerates from both above and below. As a consequence of this contamination of contraction joints by compression-resistant debris, pavements will grow longitudinally in proportion to the amount of compression-resistant debris that infiltrates and accumulates in the joints (if such growth is not resisted). Where restraint against longitudinal growth is present, the pavement will both grow and be partially compressed. But where pavement growth is prevented, pressure generation commences and continues to accumulate until either the weakest pavement joints or the must vulnerable bridge elements are fractured, thereby relieving the built-up restraint stresses. Pressure generation The generation of longitudinal pavement pressures may be visualized as suggested in Figure 2.7, which illustrated an “idealized” chart of the yearly, maximum longitudinally oriented compressive stresses, f ′c, in an extensive length of restrained pavement without movable joints (no pavement pressure relief joints or movable bridge deck joints). Initially, the stress or pressure is insignificant because the joints are relatively clean and joint seals are intact and functioning. However, as the years pass and the joints begin to fill with debris, the yearly maximum pressure increases at a growing rate. As joints continue to fill, the accumulated compressive-resistant
Chapter 2 Damage and the Pavement G/P Phenomenon
31
Figure 2.7 Hypothesized stress- or pressure-generated curve for jointed rigid pavement (brick, stone blocks, concrete).
debris minimizes infiltration of additional material, slowing the rate of joint infiltration and pressure generation. Somewhere along this hypothetical pressure generation curve, the pavement fractures adjacent to a joint, relieving some of the pressure, or the pavement blows up, relieving all of the pressure at the location of the blow-up. A number of different analytical approaches can be used to illustrate the huge compressive stresses associated with the pavement G/P phenomenon. Generally, most reasonable assumptions about measured pavement behavior will yield stresses in the range of 1000 psi (7 MPa). For a 24 ft. × 9 in. (7.3 m × 230 mm) pavement, such pressures could result in a total longitudinal force of about 1300 tons (1200 tonnes) or more than 25 times the force usually assumed in the design of bridge abutments. Blow-ups Blow-ups are unmistakable indications of high pavement pressures. As they impede the movement of vehicular traffic, their occurrence is usually reported. When they occur with considerable regularity, the numbers of them that occur within a certain period are counted. These reports serve as an indication that high pavement pressures are not local peculiarities. Instead, they indicate that high pavement pressures are, or have been before the advent of pressure relief joint use, rather commonplace. The term “blow-up” is generally understood to mean an instantaneous fracture or buckling of pavement or both. Blow-ups may be triggered by the movement of vehicular traffic, but they are caused primarily by high longitudinal compression stresses within the pavement. Compressive stresses are relieved or released by blowups (Figure 2.7a,c). The size of blow-ups has not been quantified. They can consist of minor localized joint fractures and slight buckling, major fractures with little or no buckling, and occasionally minor fracturing with significant buckling. Before 1900, the buckling (or small blow-ups) of stone block streets was probably very commonplace due to the thinness of the pavement and irregularity of block
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Integral and Semi-integral Bridges
(a)
(c)
(b)
(d)
Figure 2.8 Some pavement blow-ups of the twentieth century: (a) Ohio, about 1920; (b) Wood County, Ohio, 1963; (c) Akron, Ohio, 1975; and (d) Sacramento, California, 1998. For further documentation of these and other blow-ups, refer to Appendix 1, Table A1.
surfaces. However, with the introduction of jointed concrete pavement at the turn of the twentieth century, the G/P phenomenon began generating greater longitudinal pressures and inevitably larger blow-ups. The pavement maintenance engineer, C. D. Buck, had a clear conception of the problem when he reported his experiences with jointed concrete pavement blow-ups in Delaware in 1925 [3]. Similar blow-ups have been occurring periodically throughout the last century, some of which are illustrated in Figure 2.8.
End-jointed continuous bridges Where jointed pavements are constructed together with end-jointed continuous bridges, bridges with movable deck joints at the superstructure/abutment interface, such as the one shown in Figure 2.9, the pavement G/P phenomenon can overwhelm the abutment’s resistance to longitudinal pressures. Pavement growth can compress such bridges and move abutments (supported on other than rigid foundations) until the movable deck joints at the abutment/superstructure interface are permanently closed. Then the abutments begin to fracture. Figure 2.10 shows a close-up view of the west end of the bridge in Figure 2.9 where preliminary fracturing has taken place.
Chapter 2 Damage and the Pavement G/P Phenomenon
33
Figure 2.9 USR 52, Little Scioto River Bridge, Portsmouth, Ohio, 1964. This three-span, continuous steel girder bridge was seriously damaged by the pavement growth/pressure (G/P) phenomenon (see Figure 2.10).
Figure 2.10 Pavement growth/pressure (G/P) phenomenon damage to the Little Scioto River Bridge (see Figure 2.9). The abutment wingwall was fractured, the superstructure was lifted off of its bearings, and the girder webs were buckled. Also notice that the top of the abutment backwall in the roadway area has had prior fractures repaired with asphalt concrete.
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Integral and Semi-integral Bridges
Two rows of steel H-piles with a battered front row support each abutment of this three-span, continuous welded, steel girder bridge. Even with such stiff foundations, pavement pressures were great enough to have moved both of the bridge’s abutments 3 in. (76 mm) horizontally, permanently closing the movable deck joints at the superstructure/abutment interface. Subsequent pressures generated by the restrained growth of the approach pavements at both ends of this bridge, coupled with the restrained expansion of the bridge itself, lifted the superstructure up and off its abutment bearings, fractured the top of the abutment backwalls (notice the asphalt patches in the roadway over the abutment backwall), and fractured the wingwall. This bridge and its approaches were just 8 years old when generated pavement pressures fractured these abutments and raised the bridge’s superstructure off of its bearings. To protect this bridge from further damage, the approach pavements were cut transversely and 2 ft. (0.30 m) pressure relief joints were installed. Figure 2.11 shows what occurred during the first attempt to cut the pavement. Afternoon temperatures near the bridge site on the day of the cutting were about 80 °F (27 °C). Even with the pressure relief provided by the compressed bridge joints and fractured abutments, pavement pressures were still great enough to squeeze the saw kerf together and freeze the saw blade in the pavement. Seven months after the installation of 2 ft. (0.61 m) pressure relief joints, the east and west joints were compressed ¾ in. (19 mm) and 1⅜ in. (35 mm), respectively.
Figure 2.11 A view of the eastern approach pavement of the Little Scioto River Bridge. Pavement pressures squeezed the saw kerf closed, thereby immobilizing the saw blade during the cutting of pavement in preparation for installation of a pressure-relief joint.
Chapter 2 Damage and the Pavement G/P Phenomenon
35
The damage done by the jointed concrete approach pavement to this continuous bridge with movable deck joints at the superstructure/abutment interface is not unique. In Ohio (and presumably in many other states), there are many hundreds of such end-jointed continuous bridges, mostly built in the 1960s and early 1970s, which have been similarly damaged by jointed approach pavements that were constructed without effective pressure-relief joints. Now, however, in many states, new bridges are being constructed with pavement pressure-relief joints in their bridge approaches. Such construction should protect these new bridges from the pavement G/P phenomenon as long as such joints are properly maintained. Existing bridge approaches are also being retrofitted with pressure-relief joints not only to prevent further bridge and pavement damage, but also to protect vehicular traffic from the hazards created by instantaneous pavement blow-ups.
Integral and semi-integral bridges Where jointed pavements without pressure-relief joints are constructed in conjunction with integral-type bridges, longitudinal pressures generated by the pavement G/P phenomenon are compounded by pressures generated by the restrained expansion of the bridges themselves. Together they generate higher pressures sooner than those caused by the pavement G/P phenomenon alone. However, due to their jointless construction, integral-type bridges are considerably more resistant to longitudinal pressures than the approach pavements. Consequently, when properly designed, these bridges can usually withstand without visible distress the pressures generated by both pavements and bridges. This is the primary reason why aware and pragmatic bridge engineers favor the use of integral or semi-integral bridges where jointed concrete pavements are used. Figure 2.12 illustrates the results of the pavement G/P phenomenon and bridge expansion on the approach slab of a three-span, continuous concrete, slab integral bridge. Pavement growth and bridge expansion compressed and ultimately fractured the bridge approach slab rather than the approach pavement proper because of the unusual geometric shape of the approach slab [3]. This approach slab blowup occurred on June 28, 1971, when the approach pavement was just 15 years old. Notice that black asphalt patches are evidence of prior fractures of both the approach slab and the top leading edge of the bridge slab. As the color of the patches is so dark and uniform, and the white painted roadway edge strip does not cross the patches, the prior fractures probably occurred earlier in the month of the same year or, most likely, not more than a year earlier than the blow-up. Presumably, maintenance engineers were not aware of the reasons for these early fractures. Otherwise, on appearance of the initial fractures, they could have installed pavement pressurerelief joints that would have prevented the blow-up. Also, such a maintenance response would have protected vehicular traffic from such a potential hazard, and it would also have avoided closing the pavement to all traffic while relief joints and new approach slabs were installed. Less than a mile away, on this same highway section, where the pavement G/P phenomenon was not compounded by the restrained expansion of an integral-type
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Integral and Semi-integral Bridges
Figure 2.12 The northern approach slab of the SR 21, Barberton Reservoir Inlet Bridge, Akron, Ohio, 1956. This approach slab blow-up occurred on June 28, 1971 when this pavement was just 15 years old. The bridge is a continuous concrete slab supported by capped-pile piers and integral-type capped-pile abutments. Notice the initial transverse crack at the apex of the blowup and the asphalt patches of prior fractures (see also Figure 2.13).
bridge, the pavement structure was able to resist generating pressures for a longer period of time. Eventually, the pressures accumulated to such a level that an instantaneous blow-up occurred on June 24, 1975, 4 years after the failure of the integral bridge approach slabs (see Table A1 in Appendix 1, and Figure 2.8c). There is an interesting side aspect to the blow-up shown in Figure 2.12. Transverse cracks or fractures are quite common in the approach slabs of integral-type, continuous concrete, slab bridges as built in Ohio [4]. Numerous such bridge approach slabs exhibit transverse cracks similar to the one located at the apex of the buckled approach slab shown in Figure 2.12. In fact, these cracks are so predictable early in the life of such slabs (or slabs of similar geometric shapes and construction materials) that they could be used as crude indicators of longitudinal pressure generation in almost any type of jointed or continuous pavement. In addition these cracks (Figure 2.13) become so well defined after a brief rain shower that pressure generation in many miles of pavement could by determined by means of aerial photography alone.
Lack of awareness When considering the few representative examples of damaged pavements and bridges described in this chapter, why is the pavement G/P phenomenon, the
Chapter 2 Damage and the Pavement G/P Phenomenon
37
Figure 2.13 Approach slab of USR I-271, Wilson Mills Road Bridge, Cleveland, Ohio, 1963. Notice the transverse crack similar to the one visible at the apex of the blow-up shown in Figure 2.12. Also notice the narrow asphalt patches for prior fractures at the construction joint between the approach slab and the abutting bridge-deck slab. This photograph was taken just 7 years after construction of the approach pavement.
primary cause of this damage, not more widely recognized by bridge design and bridge maintenance engineers? Why are the characteristics of this phenomenon not more thoroughly understood by pavement maintenance and pavement research engineers? This general lack of awareness and understanding within the transportation profession is troubling. Perhaps bridge engineers do not believe that the restrained growth of jointed rigid pavements could cause such pressures, and thus such damage. This should not be considered so surprising because the major textbooks of the bridge engineering profession do not discuss, or even mention, this subject. Even AASHTO’s Standard Specifications for Highway Bridges [1], which mentions almost every conceivable force (including seismic forces that occur in century-long cycles), does not mention the forces generated by the restrained growth of jointed rigid pavement, forces that can be generated in new pavements in less than 10 years. The national Bridge Inspectors’ Training Manual has this to say about undesirable abutment movements: “The most common causes of lateral [abutment] movement are slope failure, seepage, changes in soil characteristics (e. g. frost action and ice) and time consolidation of the original soil” [5, 6]. This quote seems to hint that there may be other causes of abutment movement. However, this author does not hesitate to state that, for bridges with movable deck joints at the superstructure/ abutment interface, constructed abutting jointed concrete pavements, abutment movements due to the pavement G/P phenomenon are more common than the
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Integral and Semi-integral Bridges
movements due to seepage, slope failure, frost action, and subsoil consolidation combined. Even nationally recognized authorities on pavement maintenance, who are aware of the need for pavement pressure relief, do not appear to be familiar with the characteristics of the pavement G/P phenomenon. This unfamiliarity becomes clear when their statements about “expansion joints” are examined. For example, the following advice is given in a report about pavement pressure relief: “1. Expansion joints near structures may provide [pressure] relief to the main line pavement as far as 2000 ft. (610 m) away” [7] (italics added). Although this quote contains a small element of truth, it can be very misleading if one were to assume that this relief continued beyond a very brief time period. Just glance at the bridge details shown in Figures 2.10 and 2.12. Both these bridges were provided with two standard pavement expansion joints (1 in. [25 mm] joints filled with compressible fillers) in each of their approaches. Obviously, with respect to minimizing the effects of restrained pavement growth, these expansion joints were almost worthless. The pavement G/P phenomenon will permanently compress such joints very quickly. After being compressed, these expansion joints become merely rigid pavement artifacts incapable of minimizing additional generating pavement pressures. There are probably many other reasons for this lack of familiarity with the pavement G/P phenomenon. Probably the primary reason is the lack of specific research. As evidence of this research void, consider that the research report just mentioned above [7]. It uses the term “pressure” over 450 times in the text of the report. Also, the bibliography of the report makes reference to 149 other publications of pertinent pavement research. Yet, astoundingly, this report, which is titled “Pressure Relief and Other Joint Rehabilitation Techniques,” does not contain a single reference in its bibliography to pavement pressure-relief research. Consequently, if pavement research professionals are not familiar with the pavement G/P phenomenon, it is also unlikely that bridge design and bridge maintenance professionals would be familiar with its characteristics. Pavement pressures are obviously recognized in the few research reports that focus on their reduction and control. Also, design details for pavement pressurerelief joints are now appearing in standard construction drawings of many state, county, and city transportation departments. Still, the subject has been mentioned in only two national publications, one of which is the author’s [8], and the other is FHWA’s Bridge Inspector’s Training Manual [5]. In the latter, pavement pressure is recognized as a bridge loading but its severity is significantly understated as follows: On concrete roadways, the pavements tend to migrate toward the bridge, pressing the approach slab against the backwall. Therefore, a pavement pressure relief joint is sometimes used to relieve this additional undesirable loading. (Emphasis added)
When reading this note, while glancing at the fractures shown in Figures 2.8, 2.10, and 2.12, it is easy to recognize that bridge approach pavements do not just tend to migrate towards bridges. They in effect are being relentlessly driven against bridge abutments. Consequently, it appears that the engineers responsible for this note were really not very familiar with the pavement G/P phenomenon, the results of which they were attempting to describe.
Chapter 2 Damage and the Pavement G/P Phenomenon
39
Summary This chapter has attempted to describe the bridge damage that has come to be associated with the pavement G/P phenomenon, the phenomenon that is characteristic of jointed rigid pavements. It describes and illustrates the type of bridge damage that the phenomenon induces in various types of structures. It also documents the fact that the phenomenon is rarely mentioned in bridge design literature. Yet, because it is responsible for so much bridge damage, it is still a mystery how such a destructive phenomenon has remained unknown to so many engineers in the bridge design profession. A few apprentice engineers are made aware of the phenomenon by experienced mentors who have gained awareness and familiarity with it through their own personal experiences with damaged bridges. But without such experienced mentors to guide them, and because the pavement G/P phenomenon is not recognized in bridge design textbooks or in bridge design specifications, unfortunately every bridge design and maintenance apprentice must now learn the same bridge damage lessons that their predecessors did, and unfortunately in the same surprising way. This situation, however, could be changed by recognizing the pavement G/P phenomenon in AASHTO’s Standard Specifications for Highway Bridges [1]. This could easily be done by adding the following brief paragraph: PAVEMENT FORCES: Jointed rigid pavement approaches to bridges shall be provided with effective and long-lasting pressure-relief joints. Otherwise, bridges to be constructed abutting such pavements without pressure-relief joints shall be designed to withstand the potential longitudinal forces generated by the pavement G/P phenomenon.
Such specification recognition will improve awareness of and interest in the pavement G/P phenomenon and its characteristics, and will eventually lead to design and maintenance practices that will blunt or minimize its destructive potential. Hopefully, this specification change can be accomplished before other generations of jointed highway bridges are constructed without such protection. In the meantime, knowledgeable bridge engineers will continue to give preference to the design and construction of integral and semi-integral bridges, the bridge types that can withstand the pressure potential of unrelieved jointed concrete pavement.
References 1. American Association of State Highway and Transportation Officials. Standard Specifications for Highway Bridges, 16th edn. American Association of State Highway and Transportation Officials, Washington, D.C., 1966. 2. “What’s Wrong with the Kennedy Bridge … and How Might it be Fixed?” Louisville Courier Journal, October 24, 1991. 3. Buck, C. D., “Repair of Concrete Road Blow-ups in Delaware,” Engineering News Record, Vol. 95, No. 11, 1925, pp. 432 and 433. 4. Burke, M. P., Jr., “Bridge Approach Pavements, Integral Bridges, and Cycle-Control Joints,” Transportation Research Record No. 1113, Transportation Research Board of the National Academies, Washington, D.C., 1987, pp. 54–65.
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5. Hartle, R. A., et al., Bridge Inspector’s Training Manual, Federal Highway Administration, McLean, Virginia, revised 1995. 6. Park, S. H., Bridge Inspection and Structural Analysis, 2nd edn, S. H. Park, Trenton, New Jersey, 2000. 7. Smith, K. D., et al., “Pressure Relief and Other Rehabilitation Techniques,” Report No. FHWA/RD-86/xxx, Federal Highway Administration, McLean, Virginia, 1987, p. A-10, 8. Burke, M. P., Jr., “Bridge Deck Joints,” National Cooperative Highway Research Program Synthesis of Highway Practice, 141, Transportation Research Board of the National Academies, Washington, D.C., 1989.
Chapter 3
Integral Bridges: Attributes and Limitations
You can know the name of a bird in all of the languages of the world, but when you’re finished, you’ll know absolutely nothing about the bird. … So let’s look at the bird and see what it’s doing – that’s what counts. Richard Feynman
Introduction Integral structures, or structures without movable joints, are ages old. The most celebrated are the natural arches carved from bedrock by water and wind. The largest such structure is the Rainbow Bridge National Monument in Utah near the Arizona border (see photograph). It is composed of pink sandstone and has a span of 278 ft. (85 m). However, when considering man-made integral bridges, one cannot go much further back in recorded history than the first arch bridges made of unreinforced concrete constructed by the Romans. More recently, most are familiar with the reinforced concrete arch bridges constructed in the early decades of the last century. It began with the substitution of reinforced concrete for stone masonry in the construction of spandrel-filled arch bridges. In these bridges, the pavement and spandrel fill are supported on one or more continuously reinforced arched slabs. Although many of these multiple-span spandrel-filled arches were constructed with movable joints in their spandrel walls and railings, many of the one- or 41
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Integral and Semi-integral Bridges
two-span bridges of this type can be classified as true integral bridges because they were constructed entirely without any movable transverse joints in their arched slabs. By the third and fourth decades of last century, arch bridge construction culminated in the construction of long-span closed and open-spandrel arch bridges. Although the major supporting elements of these bridges (abutments, piers, and arch ribs) have no movable joints, they are not what could be classified as true integral bridges because they have such joints at each intermediate pier, and occasionally in the deck slabs and spandrel walls within each span. By mid-century, however, many transportation departments were building reinforced concrete rigid frame bridges. These bridges were a standard type of construction for many transportation departments. Those built in Canada by the province of Ontario are good examples. Although vertical movable joints were used between the rigid frame superstructures and their lateral wingwalls, these bridges can be classified as true integral bridges because they have no movable transverse joints in their primary supporting elements. The construction of rigid-frame bridges was paralleled by the construction of multiple-span continuous slab, beam, or girder bridges with embankments and shallow, rigidly supported, stub-type abutments. Movable deck joints were provided but only at the superstructure/abutment interface. Ultimately, the overall economy of multiple-span continuous construction made practical the use of similar bridges but without such joints at abutments. Movable deck joints at the superstructure/ abutments interface were eliminated by the use of integral stub-type abutments supported on single rows of vertically driven flexible piles (Figure 3.1). Although some versions of these bridges are now provided with movable bearings at selfsupporting piers, these are true integral bridges because they have no movable deck joints in their superstructures. Thus, although various types of integral bridges have been constructed for centuries, the designation “integral bridges” is now generally used to refer to single- or multiple-span, continuous, deck-type bridges without movable deck joints. They are generally supported by embankments with stub-type abutments on vertically driven flexible piles and by flexible piers constructed integrally with the superstructure (Figure 3.1a), or by semi-rigid piers provided with fixed and/or movable bearings (Figure 3.1b). For design engineers and engineering administrators who are considering integral bridges for the first time, a review of the brief discussions given herein should help to explain why these short- and moderate-span integral bridges are now being constructed with increasing frequency.
Attributes The popularity of integral bridges has grown with their numbers [1–3]. Originally built as a reaction to the destructive effects of leaking movable deck joints and massive pavement pressures, it soon became evident that these bridges have many more attributes and fewer limitations then their jointed bridge counterparts. Interestingly enough, these attributes not only reduced the first-cost and life-cycle cost of integral bridges, but also reduced the cost of their own future modification (e.g.,
Chapter 3 Integral Bridges: Attributes and Limitations
43
Figure 3.1 Multiple-span continuous integral bridges with stub-type abutments supported by embankments and single rows of vertically driven flexible piles. Piers can be either (a) flexible integral piers or (b) semi-rigid self-supporting piers with fixed and/or movable bearings.
widening) and eventual replacement. Consequently, integral bridges have been found to be ideal structures for state and county secondary road systems. With thoughtful design and crafting, they are becoming popular structures for rural and urban primary and interstate road systems as well. The integral bridge’s jointless construction, significant resistance to the pavement growth/pressure (G/P) phenomenon and its long-term durability has motivated bridge designers to construct such bridges at ever longer and longer lengths. For example, Ohio Department of Transportation (DOT) has recently increased its length limitation of 300 ft. (91 m) for integral bridges with skews of 30 ° or less, to longer than 300 ft. (91 m) for bridges, with lesser skews to up to a maximum of 400 ft. (122 m) for unskewed bridges. As noted in Chapter 1, Tennessee DOT recently shattered integral bridge length records by constructing the 1,175 ft. (358 m) Happy Hollow Greek Bridge of Hickman County, Tennessee (see photograph at start of Chapter 1). As discussions of attributes and limitations of integral bridges would have little significance unless they were considered with respect to those of other bridge types, the discussions that follow should all be considered relative to the attributes and limitations of similar single- and multiple-span continuous bridges with movable deck joints at superstructure/abutment interfaces. Simple design Where abutments and piers of a continuous bridge are each supported by a single row of piles attached to the superstructure (Figure 3.1a), or where self-supporting piers are separated from the superstructure by movable bearings (Figure 3.1b), an integral bridge may, for analysis and design purposes, be considered a continuous frame with a single horizontal member and two or more vertical members. When the stiffness and distribution factors are calculated for such a frame, the vertical members are so flexible compared with the horizontal member that the horizontal member may be assumed to have simple supports. Consequently, except for the design of the continuity connections at abutments, frame action of an integral bridge can be neglected when considering the effects of vertical loads
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applied to the superstructure (the superstructure can be designed assuming all movable bearings). The design of wide and relatively short integral bridges with flexible piers built integral with superstructures with concrete deck slabs is further simplified because piers and abutments generally need not be designed to resist either lateral or longitudinal loads. This is possible because the laterally and longitudinally rigid concrete deck slabs are rigidly attached to abutments and to one or more piers, and abutments are rigidly restrained by confining embankments. Consequently, essentially all lateral and longitudinal loads applied to the superstructures of such bridges are transmitted directly to abutment embankments. As a result, piers and abutments need not be designed to resist horizontal loads applied to superstructures. The design of abutment/superstructure continuity connections and transverse wingwalls can be standardized for a wide range of bridge applications. A nominal amount of reinforcement will be suitable to resist the slight live loads, dead loads, and secondary effects (shrinkage, creep, passive pressure, etc.) typical of such applications. Also, a nominal amount of reinforcement can be provided for transverse wingwalls to resist the maximum anticipated passive pressure. Once these standard details have been established, each bridge abutment can then be configured and reinforced for the vertical reactions associated with various roadway widths and span lengths. In general, this consists in no more than the determination of appropriate pile loads and spacing and pile cap reinforcement. The design of piers is similarly accomplished. Essentially all horizontal superstructure loads are transmitted to approach embankments. Also, the moments associated with pier/superstructure continuity connections are usually negligible. Therefore, piers of integral bridges (capped-pile or self-supporting types with movable bearings) need be designed only for vertical superstructure and pier loads and for lateral loads that may be applied directly to the piers (stream flow, stream debris, earth pressure, wind). Where these lateral pier loads are small, and this is usually the case, most piers, like abutments, can be designed essentially for vertical loads alone. A word of caution needs to be made with respect to flexible piers. For such piers that receive much of their lateral support from their connection to the superstructure, construction procedures are absolutely necessary to ensure that these piers are not laterally loaded until after they have been connected to the superstructure, and until after superstructure/abutment continuity connections have been completed. For example, bridge embankments must be placed and compacted before pier piles are driven if the piles are to be located in or adjacent to embankments. As the superstructure and abutment embankments resist all primary lateral loads, piers (piles, columns, footings, foundations) of wide and relatively short integral bridges may be reduced to minimum sizes and dimensions. Battered piles are not required. Fixed piers are not required. In general, pier design can be simplified to the extent that standard designs can be developed for a wide range of roadway widths and span lengths. Jointless construction The primary attribute of integral bridges is their jointless construction. To fully appreciate this attribute, one must be somewhat familiar with the performance of
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bridges with movable deck joints. For example, open joints permit contaminated roadway drainage to penetrate the joints and cause extensive below-deck deterioration. Closed joints or sealed joints give a measure of protection against bridge deck drainage deterioration. However, all movable deck joints (open, closed, or sealed) are vulnerable to the destructive effects of the pavement G/P phenomenon (see Chapter 2 and Appendix 1). Bridges with such joints constructed together with jointed rigid approach pavement have been inadvertently functioning as elaborate and expensive pavement pressure-relief joints. As approach pavements grow and the movable deck joints accommodate this growth by closing, the joints and the bridge superstructure are squeezed until the joints are fully closed. Thereafter, additional pavement growth and bridge elongation generate sufficient pressure to crush joint seals and fracture abutment backwalls and bridge seats. Consequently, the avoidance of movable deck joints obviates the need for maintenance prone joint seals and the extensive pressure damage repair that has come to be associated with them. As a secondary benefit, the avoidance of damage to movable deck joints also avoids the need for maintenance repair crews to be exposed to the hazards associated with vehicular traffic. In addition it avoids restricted traffic flow and the occasional vehicular accidents that are associated with bridge roadway repair sites. Also the smooth, jointless construction, characteristic of integral bridge roadways, improves vehicular riding quality and diminishes vehicular impact and stress levels. Pressure resistance The solid, jointless construction of an integral bridge distributes longitudinal pavement pressures by the pavement G/P phenomenon over a total superstructure area substantially greater than the approach pavement cross-section. Consequently, the smaller more fragile approach pavements are more likely to fail by localized fracturing or instantaneous buckling than the more pressure-resistant integral bridge superstructure. Unless the approaches to an integral bridge are furnished with cyclecontrol joints that are properly designed – joints that facilitate the thermal cycling of the bridge and approach slabs – they are more likely to experience early distress because the restrained elongation of the bridge also contributes to the generation of approach pavement pressure. As integral bridges are capable of sustaining significant longitudinal compression without distress, almost any pavement pressure-relief joint used specifically by maintenance forces to relieve pavement pressure would be suitable to protect them. However, bridges with movable deck joints need highly efficient pressure-relief joints if pavement pressures are to be reduced low enough to keep these joints functioning. Few such pressure-relief joints are now being used by pavement maintenance forces. Rapid construction Numerous features of integral bridges facilitate their rapid construction, and these features are probably responsible for much of the outstanding economy that has come to be achieved by their construction. Dry construction (most concrete work
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is done above stream water levels), simple members, broad tolerances, few construction joints, few parts, few materials, avoidance of labor-intensive practices, and many other features combine to make possible the completion of such structures in a single short construction season. Such rapid construction becomes particularly important when collapsed bridges or seriously damaged bridges must be replaced in the shortest possible time. Also, this rapid construction becomes particularly advantageous when bridges carrying high volumes of traffic must be replaced in two or more construction stages. As noted above, such rapid construction is possible because of the many simplifying features that are characteristic of most integral bridges. These include but are not limited by the following. Embankments Embankments can be placed and compacted with large earth-moving and compaction equipment. Only limited use of hand-operated compaction equipment is needed. Cofferdams Integral bridges, especially those constructed with capped-pile or drilled shaft piers, can be constructed with fewer delays resulting from inclement weather and stream flooding. Abutment excavations and pile driving near the top of abutment embankments can be done without cofferdams and generally without the need for dewatering. Foundation construction can progress as fast as pier and abutment piling can be driven. Subsequently, pile cap construction and erection of precast or prefabricated superstructure members can proceed with little regard for stream water levels. Small excavations Abutment excavations need be no more than 2–3 ft. (0.6–0.9 m) deep. Vertical piles At an abutment, vertical piles can be uniformly spaced and driven in a single horizontal row. In contrast, the typical non-integral abutment foundation consists of two or more rows of both vertical and battered piles. Pier piles These can be uniformly spaced and driven in a single horizontal row. This arrangement avoids the need for pile clusters with some battered piles for each column footing, the typical pier foundation for many cap and column piers of jointed bridges. For bridge sites with high water levels, driving piles for pier footings of jointed bridges is more difficult because piles must be driven inside cofferdams.
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Simple forms Pier and abutment pile caps are quickly formed because they are usually composed of simple rectangular shapes. Few joints Few construction joints are used for integral bridges. Consequently few concrete placement and curing days are needed. For example, no more than four concrete placement days are needed for most integral bridges. Only one day each is required for placing pier caps, continuity connections, deck slab, and approach slabs. Actually, single-span integral bridges in some states have been further simplified to the extent that only 2 days are required: the second day is necessary only to place separately cast approach slabs. In contrast, constructing most jointed bridges requires 5 or more placement days and subsequent curing days. Few parts Fixed and movable bearings, armor for bridge deck joints and joint seals are unnecessary. The normal delays usually associated with movable joint installation and adjustment, and anchor bar placement are avoided. Broad tolerances The close construction tolerances usually associated with jointed bridges are not necessary for integral bridges. For example, the elevation, slope and uniformity of bridge seats are not important because only rough surface construction joints are required. Reduced removals Using typical multiple-span integral bridges with embankments and stub-type abutments to replace shorter bridges with wall-type abutments permits new bridges to be constructed without requiring the complete removal of existing substructures. New bridges can be configured to straddle existing foundations (Figure 3.2). Where existing abutments are located in new embankments, most of existing abutments need not be removed. At many sites, significant savings are possible. For example, where normal water levels are high, complete removal of existing substructures could require the building of large cofferdams for this purpose alone. Simple beam seats Some of the labor-intensive practices required for jointed bridge construction are either eliminated or substantially simplified in integral bridge construction. For example, consider the problem of providing appropriate bridge seat surfaces
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Figure 3.2
New continuous integral bridge straddles old foundations.
for the elastomeric bearings of side-by-side and spread box beam-jointed bridges. Side-by-side box beams of jointed bridges must be canted laterally to match the deck crown and tilted longitudinally to accommodate bridge grade. Also, as the ends of these beams are sloped owing to residual camber, adjustments usually need to be made in beam bottoms, bearings, or bridge seats to compensate for these geometric irregularities and provide parallel loading surfaces for elastomeric bearings. A number of options are available to the designer: 1. 2. 3.
A longitudinally tapered recess can be cast in beam bottoms to match a longitudinally level and laterally crowned bridge seat surface. Bridge seats can be sloped to match the orientation of beam bottoms. Tapered metal laminates can be molded within the bearings to compensate for differences in the longitudinal orientation of beam bottoms and seat surfaces, and bridge seats can be laterally crowned to match the canted beams.
If this is not complicated enough, the specific provisions adopted to compensate for crown, grade, and camber may, in some bridges, have to be unique for each bridge seat because bearing orientation changes from one substructure to the next as a result of changes in grade and span lengths. In addition, poor estimates of residual camber, differences in residual camber from beam to beam, skew effects, errors on computing actual surface orientations, and errors in construction make the attainment of parallel-loading surfaces uncertain. Consequently, even after all of these considerations have been accounted for, occasionally it is necessary to use shims under elastomeric bearings to obtain solid seating of beams on bridge seats. On the other hand, integral bridge construction makes most of these considerations and procedures unnecessary. As box beams of integral bridges need only temporary support until continuity connections between the superstructure and abutments have been casts, a narrow temporary elastomeric erection strip can be used on a temporary construction joint surface to support the beams (Figure 3.3a). Then after continuity connections are cast and cured, because of the relative deformational characteristics of elastomeric erection strips and fully cured continuity connection concrete, all of the beam reactions (dead load, live load, and impact) will be uniformly supported by the rigid cast-in-place continuity connections and not by the compressible elastomeric bearings. These relative rigid connections are,
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Figure 3.3 Capped-pile stub-type abutments for integral bridges: (a) for prestressed concrete box beam stringers with temporary elastomeric erection strips; or (b) for steel I-beam stringers with temporary support bolts.
in addition far superior in supporting superstructure loads compared with a series of separate and uncertainly loaded elastomeric bearings that are characteristic of jointed box beam bridges. As concrete or steel I-beams are placed vertically, crown effects need not be considered when appropriate bearings and bridge seats are provided. However, even for I-beam bridges, integral construction with its continuity connections considerably simplifies bridge seat preparation and temporary bearing requirements and improves the distribution of superstructure reactions (Figure 3.3b).
Elimination of bearing anchor bars For typical jointed bridges, superstructures are usually attached at one or more substructure elements, usually at an intermediate pier. For side-by-side prestressed box beam bridges, this attachment is often done by placing anchor bars down through precast holes in the box beams and into field-drilled holes in the bridge seats. As a result of the construction uncertainties regarding beam lengths, and substructure locations, holes in the bridge seat must be field drilled after all of the beams have been placed and laterally compacted together. Considering the dimensional errors that are likely to occur in accurately locating substructures and in placing primary reinforcement in the pier caps, it is reasonable to assume that some of this reinforcement will be cut during field drilling of the anchor bar holes in the bridge seat. As superstructures of short box beam integral bridges receive their lateral and longitudinal support from abutment embankments, only flexible piers not integrally constructed with the superstructure (the type of piers that depend upon the superstructure for lateral and longitudinal support) need to be provided with anchor bars and field-drilled anchor bar holes. All other pier types (flexible integral piers and self-supporting piers with movable bearings) do not need bearing anchors
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and field-drilled anchor bar holes. Consequently, the damage usually associated with field drilling of anchor bar holes is avoided with these pier types. Of particular significance is the savings in time and costs made possible by eliminating the labor-intensive procedures of drilling and cleaning bar holes and placing grout and anchor bars. This savings in time and costs can be significant where project plans require anchor bars for every beam and for every support. Eliminating field drilling for anchor bar holes becomes particularly important in some bridge modification projects. For example, in replacing only the superstructures of existing bridges with new box beam superstructures (and this type of bridge modification project is occurring with increasing regularity), conversion of jointed bridges to integral bridges with cast-in-place continuity connections at abutments enables designers, when working with self-supporting piers, to provide elastomeric bearing pads without anchor bars. Fixed bearings and anchor bars are not required. By eliminating anchor bars and the need for field drilling of anchor bar holes, designers can not only accelerate construction, but can also ensure against the possibility of damaging existing primary pier cap reinforcement. Broad span ratios The ratio of end span to center span of continuous bridges (Le/Lc) is generally set at or near 0.8 to achieve stable superstructures and a balanced beam design, a design where the maximum positive moments in all spans are approximately the same. This is the ratio that is most often used for stream crossings. Lesser ratios are often used for grade separation structures where short end spans are needed to achieve the shortest practicable bridge length. However, for sites where span ratios of less than 0.6 are required for jointed bridges, provisions usually need to be made to prevent beam uplift during deck placement and uplift due to the movement of vehicular traffic. Such provisions can become complex and expensive when bearings must be provided that will allow horizontal movements of the superstructure but at the same time prevent superstructure uplift. Integral bridges, on the other hand, are more resistant to uplift because the weight of abutments resists uplift. Thus, a span ratio of 0.5 can be used without any change in integral bridge design details. For the smallest span ratios, a procedure for deck slab placement can be used to counteract uplift during construction. Earthquake resistant As the decks of integral bridges are rigidly connected to both abutments and consequently to both embankments, these bridges are in fact part of the earth and will move with the earth during earthquakes. Consequently, when integral bridges are constructed on stable embankments and subsoils, they should have an adequate response to most earthquakes. For a bridge that is to be located across a fault line – a highly unlikely situation – differential lateral movement of the ground at the fault line during an earthquake could seriously stress and possibly collapse the superstructure. However, an integral bridge with a steel beam or steel girder superstructure should be able to survive such unusual ground movements without collapse.
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Simplified widening and replacement Many bridges placed on the highway system in the past were designed for immediate needs without much thought being given to future bridge modifications that would be necessary to accommodate substantially higher traffic volumes and vehicular weights. Through arches of reinforced concrete, through trusses of steel, and bridges with wall-type abutments with flared wingwalls are prime examples of such bridges. Most often, through structures have to be completely replaced when increased traffic speeds and traffic weights necessitate building wider roadways and stronger structures. Widening bridges with wall-type abutments and especially those with flared wingwalls is complex and relatively expensive. In contrast, integral bridges with straight capped-pile substructures are convenient to widen and easy to replace if future demands have not been accurately foreseen. Of particular significance is the fact that their substructures (the piling) can be recapped and reused or, if necessary, they can be withdrawn or left in place. Such bridges avoid the necessity of building expensive foundations that interfere with the placement of future foundations. Many of the stream crossings in Ohio – and presumably the same is true for many states and provinces – have been spanned by at least three earlier bridges, with a fourth bridge presently being planned. For many of these earlier removed bridges, the foundations have been left in place. Consequently, when planning today’s replacement structure for small stream crossings, design engineers find that parts of these streambeds are filled with these old foundations. However, with the use of capped-pile integral substructures, the new substructures can usually be placed to clear existing foundations and avoid the expense of removing them. Also, the greater span ratio range makes integral bridges greatly adaptable for foundation-filled bridge sites. Live load distribution Superstructures that are integrally constructed with capped-pile abutments and piers instead of separated from them by numbers of compressible elastomeric bearings give vehicular wheel loads broader distribution than would otherwise be possible. This arrangement reduces superstructure service load stresses. The attributes noted above make integral bridges very desirable structures. However, this desirability has been attained at the expense of a number of limitations, and these limitations should be recognized so that design engineers can evaluate them when considering the use of integral bridges for specific applications.
Limitations Pile stresses Except for abutment piling and wingwalls, the various members of integral bridges are subjected to essentially the same levels of primary stresses (dead load, live load, impact, etc.) and secondary stresses (shrinkage, creep, thermal gradients, etc.) as their jointed bridge counterparts. But because of their flexural resistance, the
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vertical piling of integral bridge abutments will resist the lengthening and shortening of bridge superstructures responding to temperature changes. Consequently, the piling of long integral bridges can be subjected to flexural stresses considerably greater than those of their jointed bridge counterparts. For long integral bridges, research with abutments supported by steel piles has shown that abutment piling stresses can approach, equal, or even exceed the yield strength of pile material. Such piling stresses, if they are large enough, will result in the formation of plastic hinges that will limit the flexural resistance of the piling to additional superstructure elongation. At the same time, laterally supported piling should retain their capacity to support full vertical loads. As piles of integral bridges may be subjected to high flexural stresses, only suitable pile types should be used for these applications. Such piles should retain sufficient axial load capacity while localized pile transformations occur that will reduce their resistance to bending. For this reason, only steel H-piles or appropriately limited and reinforced prestressed concrete piles should be used to support abutments of the longer (≥300 ft. [≥91 m]) integral bridges. Some very informative pile-test research has recently been conducted to document the structural adequacy of these pile types for integral bridge construction [4, 5], particularly Federal Highway Administration Report [5]. The tests illustrated how common pile types performed successfully even at stress levels considerably beyond what is normally permitted for non-integral types of construction. For short integral bridges (20 years). However, such large sustained pressures will ultimately cause pavements to fail instantaneously as illustrated in Figures A1.5 and 2.8. Pavement growth An examination of the behavior of pavement pressure relief joints and adjacent pavements helps to explain the behavior of a pavement structure such as that illustrated in Figure A1.3 (curve a), after it has experienced a catastrophic blowup. The behavior of such a pavement is similar to what would be expected after the installation of a pressure-relief joint, or immediately after the completion of a bridge with movable deck joints at the superstructure/abutment interface. At the Stanley Avenue Bridge in Dayton, Ohio, concrete approach pavements were cut transversely so that 3 ft. (0.91 m) wide bituminous-filled pressure-relief joints could be installed (Figure A1.6). The need for these relief joints became necessary when the movable deck joints at the superstructure/abutment interface were found closed and evidences of substantial longitudinal pressure were evident. Periodic observations of these relief joints were made over a 5-year period. The cutting of pavements (and the release of pressure) was followed by a gradual and progressive closure of the relief joints. At one of the two joints, for instance, the movement of the approach pavement into the joint amounted to 7½ in. (190 mm). As this movement occurred over a 5-year period, an average pavement growth rate of 1½ in. (38 mm) per year was experienced. The approaches to this bridge consist of two pairs of two 12 ft. (3.66 m) wide pavements with a separately cast 4 ft. (1.22 m) wide raised median between them. When the pavements and separate median were constructed, the pre-sawed contraction joints were placed to coincide with the vertical joints in median curbs. The longitudinal movement of pavement was manifest not only by compression of the relief joints, but also by a differential movement of pavement joints in relation to median curb joints. Joints closest to the bridge showed the greatest differential
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Figure A1.6 The rear approach roadway of the Stanley Avenue, B&O Railroad Bridge, Dayton, Ohio, 1960.
movement – 7½ in. (190 mm) – while joints further removed from the bridge showed progressively less movement, with joints located approximately 1,000 ft. (300 m) from the bridge showing no appreciable movement. Consequently, based on behavior of pavement approaches to the Stanley Avenue Bridge, and to similar pavements of many other bridges, it appears that up to 1,000 ft. (300 m) or more of pavement can contribute to movement of pavement at pressure-relief joints. As these pavement movements are both progressive and accumulative, and as a substantial length of pavement contributes to this movement, it has come to be called “growth” to distinguish it from “expansion,” the term usually used to refer to the minor component of temperature-related cyclic movement. Pavements with pressure relief joints experiencing growth are also subjected to substantial pressures. However, instead of relatively constant pressures being distributed throughout an extensive length of jointed pavement, as is typical of the restrained pavement illustrated in Figure A1.1c, pressures vary linearly along the length of pavement experiencing growth. Pressures are minimal at pressure-relief joints. (They equal the resistance of relief joints to compression, the pressures indicated by the relatively flat portion of curve b in Figure A1.3.) They approach a maximum at a pavement pressure plateau located at some distance (±1,000 ft. [300 m]) from relief joints. Pavement between these two boundaries will continue to grow toward relief joints, with most growth occurring at relief joints and progressively less growth at distant locations (± 1,000 ft. [300 m]) where maximum residual pressures have been maintained. Between these two limits, pavement will continue to grow toward relief joints until the relief joints are closed. Thereafter, with pavement being restrained from further growth, pressure generation increases (Figure
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A1.3, curve b) within the lengths of formally growing pavement until increasing pressures are relieved by progressive fracturing of pavement joints, blow-ups, or the replacement or modification of formerly closed relief joints. Movable bridge deck joints The behavior of pavements adjacent to continuous bridges provided with movable deck joints at the superstructure/abutment interface is similar to that of pavements adjacent to pressure relief joints (Figure A1.3, curve b). As bridge abutments are not designed to resist the huge pressures characteristic of restrained pavements, approach pavements will grow toward jointed bridges, jamming abutments toward superstructures and progressively closing the movable deck joints. Subsequently, after the deck joints are closed, pavement pressure generation continues to increase until it reaches high enough levels to begin fracturing pavements, abutments (Figures A1.7 and A1.8), or rigid bridge piers. In this context, pressures generated by the restrained growth of approach pavements are compounded by pressures generated by the restrained expansion of bridge superstructures. Supplementing each other, they cause both pavement and bridge distress and fracturing earlier than would have been expected from the restrained growth of approach pavements alone. Generation of pavement pressure and the generation of pavement growth appear to be two sides of the same coin, or two major aspects of the same phenomenon. Debris infiltration of contraction joints will result in pressure generation where
Figure A1.7 USR I-90, 140th Street Bridge, Cleveland, Ohio, 1976: This fourspan, continuous deck-type, steel-beam bridge with movable deck joints at the superstructure/abutment interface, along with similar companion bridges on the same route, was seriously damaged by the pavement G/P phenomenon (see Figure A1.8).
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Figure A1.8 This view of an abutment bridge seat of the bridge shown in Figure A1.7 illustrates how the pavement G/P phenomenon jammed the stubtype abutments (founded on two rows of piles) at least 3 in. (75 mm) into the superstructure. Subsequently, the generated pavement pressures and bridge superstructure expansion jammed the abutments under the movable deck joint armor, thus raising the superstructure up and off of the rocker bearings, and the superstructure’s dead- and live-load reactions on the abutment backwalls were great enough to shatter the backwalls.
pavements are restrained (no pressure relief joints or movable deck joints (Figure A1.3, curve a), or growth generation where pavements are not restrained (with relief joints or movable deck joints). In many instances, growth will take place until all available space has been consumed. All available space refers to space provided in pavement expansion joints, space available in pressure-relief joints by compression of the filler, and space provided in movable bridge deck joints. Then, as pavements are restrained from further growth, pressure generation commences along the second portion of the pressure-generation curve (Figure A1.3, curve b). As both pressure and growth generation appear to be directly related to debris infiltration of contraction joints, it goes without saying that the factors that have a significant effect on pressure generation have a similar effect on growth generation. Ideally, the solution to this problem is simple. All that is needed is a pavement contraction joint design that would completely seal such joints against the intrusion of all foreign materials, even at the lowest site temperatures. Designs that are somewhat less than ideal would be suitable because a reasonable service life could be attained. However, it should be clear that current technology is not sufficiently developed to provide a cost-effective solution to the significant problem of debris infiltration of contraction joints.
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Many of these words were written over 30 years ago. At that time, pavement and bridge maintenance engineers adopted programs to install pavement pressure-relief joints to control stress levels and protect both structures and vehicular traffic from the adverse consequences of pavement pressure generation. However, as described and illustrated below, a few current pavement research and maintenance engineers are proposing an entirely new direction for pavement maintenance, a direction that appears to ignore the major characteristics of the pavement G/P phenomenon, and the inevitable consequences of allowing generating pressures to reach destructive levels. Unfortunately, if this new direction is accepted by pavement maintenance agencies, this author predicts dire consequences in the not too distant future for the transportation profession in both human and monetary terms.
New direction commentary Wisconsin research In a series of recent papers (1996–1997), the engineers of Wisconsin Department of Transportation (DOT) have preached the use of unsealed contraction joints. In the most recent paper of this series [2], it continually stressed that the primary objective of all joint sealant research should be total pavement performance and not merely sealant performance. However, when examining this latest report, it was found that the evangelist is guilty of the sin that is condemned. Like most prior joint sealing research that is disparaged as being too narrowly focused, the same can be said about current Wisconsin research because it completely ignores the effect of unsealed joints on the generation of pavement pressures. Wisconsin’s latest report was for five 1,000 ft. (300 m) long pavement test sections with ages of 8, 13, and 22 years. The report concludes with several statements to the effect that joint sealing has no significant effect upon pavement distress or life, upon material integrity, or upon ride quality. It is also stated that blow-ups are a function of joint spacing and not joint sealing. Although many pavements reach the age of 10–15 years without visible signs of pressure-related joint distress, it would be unusual, but not unexpected, that Wisconsin’s 8- and 13-year-old unsealed test sections could reach these ages without visual signs of compression joint damage. But it would be remarkable for a 22-yearold pavement to reach such an advanced age unscathed. Consequently, it was not surprising to learn that these older test sections had in fact been modified with a number of full-depth repairs. John W. Bugler, a former pavement maintenance engineer for the New York State DOT, examined Wisconsin’s test pavements a number of times over the last two decades. During one of these examinations he found that five full-depth lane-width repairs were made to the “unsealed” 20 ft. (6.1 m) test sections of USR 51, the oldest test section reported upon in the paper. Pavement markings indicated that these repairs were made in June, July, and August (the hottest months) of 1993, at the time when pavements had aged 19 years. Although the research principal claimed that this section of pavement experienced premature joint spalling due to an irregularity in the location of reinforcement, two pavement joints (identified as joints
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37 and 41 on the test pavements) appeared to have been in very good condition in 1987, just 6 years before their full-depth repair. Consequently, although misplaced reinforcement may have contributed to distress at some joints, it appears that high compressive stresses were probably responsible for most distress that necessitated the full-depth repairs to this oldest unsealed test section. It is instructive to note that, in 1993, there were no full-depth repairs made to a companion sealed test section (N4F), even though it presumably was constructed at the same time, by the same contractor. Also, apart from the sealed joints, it had a similar design and was exposed to similar weather extremes, traffic volumes, and truck loadings. Therefore, it appears that the reported results of Wisconsin’s research on unsealed pavements were inconclusive because there was no attempt made to monitor and report about the relative magnitude of generated pavement pressures for both the sealed and the unsealed pavement test sections. As a result, joint sealing recommendations coming from this research are of questionable validity. As there are 50 state transportation departments that have adopted their own sealing practices with respect to the maintenance of jointed concrete pavements, why should this author (and his colleague, John Bugler) be so concerned about the pavement maintenance recommendations originating from a single state like Wisconsin? The reason for the concern was the fact that Wisconsin was recommending the adoption of unsealed pavement contraction joints, a recommendation that was contrary to the generally accepted sealing practices of most States and to the practices that were recommended by most authoritative pavement maintenance specialists, and, as described above, because that recommendation was based on the complete neglect of the pavement G/P phenomenon and its destructive potential with respect to both pavements and bridges. Nevertheless, Wisconsin’s pavement maintenance recommendations were given particular significance by pavement engineers of the Federal Highway Administration (FHWA) who were, without any other research justification, promoting the adoption of Wisconsin’s unsealed pavement practices by other state transportation departments, including those of Ohio and New York. That is the reason why the unfortunate Wisconsin episode has demanded recognition and a brief elaboration in this appendix on the pavement G/P phenomenon. Pressure-relief joints Some pavement researchers appear to have an ambivalent attitude with respect to the efficacy of pressure relief joints. They define a pressure relief joint as “a transverse joint installed to relieve compressive stress for the purpose of reducing deterioration of existing joints, pavement blowups, and protecting abutments” [10, p. 3]. In this definition, there appears to be a vivid recognition that pavement compressive stresses and pressures are primarily responsible for both pavement and bridge damage, and that pressure-relief joints, as their name implies, are intended to prevent such damage by moderating pavement pressures to tolerable levels. On the other hand, they also state that “Because they provide no load transfer, deflections at the relief joints tend to be high. Significant pumping, faulting, corner brakes, and slab deterioration can thus occur in the vicinity of a pressure relief joint.” They unfortunately conclude these statements by recommending that: “Pressure relief
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Figure A1.9 Performance of a foam-filled pavement pressure relief joint [9, p. 32], with a clarifying detail added by the author.
joints should be used only on pavements which have experienced blowups or are pushing bridges” [10, p. 25]. Even though they recognize the relationship between high pavement pressure and pavement and bridge damage, they caution against the early use of pressure-relief joints. In other words they seem to be suggesting that patients with high pressures should not be treated until after the patient has experienced a life-threatening rupture. Such a prescription is questionable to say the least. That same report contains a number of informative charts of relief joint measurements which illustrate the response of such joints (polymer-foam-filled joints 4 in. [100 mm] wide) to the pressure-generated growth of pavement. Figure A1.9 is one such chart and can be considered somewhat idealized but nevertheless typical for applications of foam-filled pressure-relief joints that were initially 4 in. (100 mm) wide. Notice that the joint width is progressively compressed during the hot summer months and attains almost complete closure in about 3 years’ time. Subsequently, as the joint is fully closed, it will function to restrain pavement growth and thus permit the subsequent generation of higher pavement pressures as indicated by curve b in Figure A1.3. However, astoundingly, the report concludes with the recommendation that “most new pressure relief joint widths should be limited to 1 to 2 in. (25 to 50 mm) (maximum) to reduce the possibility and severity of over-relieving the pavement” [10, p. 124]. As indicated with respect to Figure A1.9, such a recommended joint width would have an effective service of only a year or two, after which it would have to be replaced periodically to prevent pavement pressures from reaching destructive levels. As most individuals would recognize the adverse economical and political consequences of closing pavement lanes to traffic every couple of years
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merely to replace such short-lived relief joints, could such a recommendation suggest that these researchers incorrectly assume that placing a relief joint terminates the pressure generation process?
Contraction joint spacing In the introduction to the final report of the research project “Pressure Relief and Other Joint Rehabilitation Techniques,” the following statement is given: Most of these problems [sealant deterioration, intrusion of incompressibles, concrete deterioration, etc.] are associated with long-jointed reinforced concrete pavements, and not with short-jointed plain concrete pavements. [10, p. 1]
On page 13 of the same report [10], the following statement is given: Pavement growth due to intrusion of incompressibles produces far more severe problems in pavements with long slab lengths. States such as California which have thousands of miles of short-jointed pavement (i.e., slab length less than 20 ft. [6.1 m]) rarely experience blowups. States such as Illinois, Michigan, and Virginia which have 40 to 100 ft. [12.2 to 30.5 m] slabs frequently experience blowups.
Current reports from Wisconsin reflect this view: Incidentally, blowups were a major problem in Wisconsin for pavements with 80 and 100 foot (24 and 30 meter) joint spacing. The use of closer spacing (15 to 20 feet [5 to 6 meters]) has virtually eliminated blowups. [1, p. 6]
The problem with these statements is that they imply that pressure generation. and consequently pressure-related pavement distress such as spalling, fracturing, and blow-ups. can be avoided by reducing just the joint spacing from about 80– 100 ft. (24–30 m) down to 15–20 ft. (5–6 m). Such recommendations completely ignore the numerous other factors that significantly influence joint infiltration (and pressure generation) such as ambient temperature range and duration, sealant quality and maintenance, rainfall, porosity of subgrade and subsoils, etc. They also conveniently ignore the potential long-term consequences of using pavements with a short contraction joint spacing. Assuming that all aspects of pavements are the same except for joint spacing, this author thinks that it is improbable that pavements with the “long” spacing will blow up whereas the pavement with the “short” spacing will not. Structures do not operate on the basis of good or bad; they operate in a continuum. Consequently, it very well may be that as joint spacing diminishes, joint shrinkage cracks will become smaller and, depending upon particle sizes of compression-resistant debris, debris infiltration and consequently pressure generation may be slowed. However, ultimately, pressure generation will reach such levels that blow-ups will occur in both long-jointed and short-jointed pavements, one later than the other. For example, how else can one account for the growth and blow-ups of brick and stone block streets that have joint spacing of only 6 in. (150 mm) or less?
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Bridge damage Pavement and bridge engineers have different experiences and consequently different attitudes about the effect of pavements on abutting bridges. A glimpse of these attitudes may be gained by examining the terminology that they use when they talk or write about this subject (emphasis added): Another problem caused by pavement growth is bridge pushing … the pavement will push against the bridge approach slabs. Incidents of cracked abutments and bridge decks being pushed nearly off the abutments have been documented … . [10, p. 7] Pressure relief joints should be used only on pavements which experienced blowups or are pushing bridges. [10, p. 25]
In addition to “pushing,” other pavement researchers use the terms “shoving” or “thrusting.” In contrast, consider how they feel when they are speaking about other pavement devices. Many other types of secondary structures can also be damaged by pavement growth. These include manholes and other drainage and access structures in the pavement surface. They can be crushed, collapsed, or rendered nonfunctional as they are moved by the pavement. Curbs and traffic islands are also subject to shattering, breakup, upheaval, and failure as the surrounding pavement expands. [10, p. 7]
Notice, with respect to bridges, that they say “push,” “shove,” or “thrust.” But with pavement items they say “crushed,” “collapsed,” “shattered,” “breakup,” etc. Obviously, these researchers have not had the opportunity to examine bridges that have been compressed by high pavement pressures. In bridge engineers’ terms, abutments and fixed piers are “fractured,” backwalls are “crushed,” girders are “buckled,” bearings “displaced,” etc. In Wisconsin, bridges were not even an issue. In evaluating of the relative efficacy of sealed or unsealed pavement joints, pavement maintenance engineers qualified their research as follows: Wisconsin’s research relates to PCC highway pavement slabs on grade; it does not consider airfields, interior slabs, buildings, bridges, etc. [2, p. 15]
Notice the sequencing of the items in this list. It appears that these researchers think of bridges as isolated and completely independent structures like “airfields,” “buildings,” “interior slabs,” etc., and not as integral parts of a highway facility that could affect and be affected by pavement behavior. Incidentally, the offending statement quoted above was subsequently modified in the published report after criticism of the original report by this author. Although Wisconsin engineers did not consider bridges in their evaluation of pavement performance, they were well aware that pavement compressive stresses could reach high levels. With respect to such stresses, they state that pavement stresses “can only amount to 7,000 to 14,000 kPa (1,000 to 2,000 psi) maximum, well below the compressive strength of concrete” [2, p. 30]. These are significant stresses, even for concrete pavement. However, with respect to bridges, such pressures from
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239
a two-lane pavement could amount to from 25 to 50 times the force that stub abutments are designed to resist. In bridge terms, such forces are irresistible. Consequently, where pavement engineers ignore the potential for high pavement pressure against bridges, serious bridge damage could be the result. As bridges with movable deck joints have functioned as huge and expensive pavement expansion joints [3], they have been progressively closed by the pressureinduced growth of jointed pavements. Subsequent to such closure, bridges have experienced severe damage due to the combined effect of the response of restrained pavements and abutting bridge decks to high temperature levels. Pragmatic bridge engineers have become aware of the apparent futility of constructing bridges with movable deck joints adjacent to rigid pavements. Consequently, they are now electing in increasing numbers to construct integral bridges (jointless bridges), which are significantly more resistant to pavement pressures. Such a response to jointed bridge damage can compound the pavement engineer’s problems if such bridges are constructed without suitable joints in bridge approaches. Otherwise, in the future, blow-ups will become more commonplace on bridge approaches. Pavement expansion joints Two quotes from recent pavement research literature help to illustrate that some pavement research engineers fail to understand the performance of pavement expansion joints when such joints are located in pavements that are under pressure. Construction of expansion joints is currently recommended only when major blowups or other pressure-related damage has occurred. [10, p. 25] Bridge approach expansion joints will usually provide sufficient pressure relief within 500 feet (150 meters) and additional relief is not needed. [10, p. 25]
First, as typical pavement expansion joints are designed to provide for relatively small cyclic thermal movements, their use as pressure-relief devices in pavements being subjected to progressively higher and higher pressure is inappropriate. Generating pavement pressure will close such devices within a year or two, after which they will become merely rigid pavement artifacts incapable of further extension or compression. Second, with respect to both statements, how can a class of objects be safely recommended for use based upon its generic name only? Does the joint width and filler type not have some significance in this respect? For example, a 1 in. (25 mm) wide joint filled with asphalt-impregnated cane will, when subjected to compressive stresses, close to such an extent in 1 year’s time that it would be completely ineffective in relieving subsequent pavement pressure. Foam-filled pressure-relief joints in widths of at least 4 in. (100 mm), or asphalt-filled relief joints 12 in. (300 mm) or wider, are intended specifically for this purpose. Expansion joints in compressed pavements are beneficial in only one respect. Their somewhat elastic type of filler helps to minimize localized stress concentrations and thereby protects pavement joints from localized spalling and fracturing. But they will not, as apparently some pavement engineers believe, prevent the generation of pavement pressures.
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Pavement research Most pavement professionals recognize that, in addition to reactive aggregates, it is the contamination of contraction joints by compressive-resistant debris that is responsible for the development of pavement pressures and associated joint distress such as spalling, fracturing, and blow-ups. They also recognize that the G/P phenomenon takes up to 8 or more years for pressures to reach levels where distress becomes manifested. Consequently, it was distressing to learn that a new pavement research project was initiated by the Ohio DOT with the encouragement of the FHWA to, in part, evaluate the relative efficacy of sealed or unsealed contraction joints throughout a pavement service life of only 5 years. In addition, it was also learned that the monitoring of pavement stresses and pressures was not to be a part of this project [11]. As one of the primary purposes of sealing contraction joints is to retard the generation of destructive pavement pressures, it appears ludicrous to this author to try to compare the relative efficacy of sealed and unsealed contraction joints without monitoring their effect on the pavement pressures that they are intended to control. Also, as this project was programmed for only 5 years, the period illustrated by the initial flat portion of curve a in Figure A1.3, how could the researchers accurately determine differences between the pressure-generation curves for the pavements with sealed contraction joints or the pavements with the unsealed contraction joints, or predict the ultimate effects of these differences? Since such research requires clairvoyance and speculations to achieve useful results, it must be considered bad science at best and pseudoscience at worst.
Summary As discussed in this chapter, the focus of recent pavement research on pavement joint design and maintenance is startling to engineers who recognize that high pavement stresses and pressures are responsible for most of the progressive damage suffered by jointed pavements and abutting bridges. For example, one of the most comprehensive recent examinations of current pavement maintenance practices [10] uses the term “pressure” over 450 times. That is correct, more than 450 times as counted by this author. Also, the report for this project contains an extensive bibliography of 149 references to other papers of pertinent pavement research. Yet, remarkably, this bibliography did not contain a single reference to research that focused on the generation of pavement pressure. Another recent report about extensive research on sealed and unsealed pavement joints [2] did not mention the term “pressure” once, although it is widely recognized that joint performance is one of the primary factors that affect the generation of destructive pavement pressures. To put it bluntly, it appears that some current pavement researchers are not making any attempt to envision events occurring beyond the realm of ordinary sense perceptions. With respect to the effect of the G/P phenomenon on bridges that abut jointed pavement, some researchers ignore bridges entirely or assume that some device named “expansion joint” will somehow magically protect a bridge from the
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inexorable pavement growth, and subsequently from the crushing pressures that are characteristic of such pavements. Others minimize pavement/bridge interaction by using such terms as bridge “pushing,” “shoving,” or “thrusting” to help avoid the recognition that jointed pavements and abutting bridges are self-destructing. With respect to the relationship between jointed pavement design and maintenance, and the generation of pavement pressure, many pavement maintenance engineers intuitively recognize that there are at least a dozen factors that influence pavement pressure generation and high pressure levels. Yet the relative significance of these factors has not been demonstrated by research that controlled these factors and measured pavement strains and/or pressures. Without controlled monitoring of the G/P phenomenon, pavement design details and maintenance practices will continue to depend upon the advice of presumed “authorities.” Unfortunately, the transportation profession will then continue to base its decisions on personal philosophies and flawed assumptions, and not on scientifically demonstrated and replicated proof. Contrary to the recommendations of some current pavement research authorities, generating pavement pressures should not be allowed to reach destructive levels. Otherwise, the transportation profession will continue to be familiar with pavement fracturing (see Figures A1.4, A1.5, and 2.8), bridge fracturing (see Figures A1.8, 2.2, 2.4, 2.6, 2.10, and 2.12), restricted traffic flow at bridge repair sites, vehicular accidents, and personal injury. There is a better way. Simple methods should be devised to monitor the generation of longitudinal pavement stress and pressure levels, the relative significance of the factors that affect contraction joint behavior and the generation of pressures should be established, and design details and maintenance practices should be devised that will retard pressure generation and limit or control generated pressures to tolerable levels. Then pavement design and maintenance will be given a different direction, a direction that should produce a significantly more durable and safer highway environment for those who have entrusted the transportation profession with their welfare.
Acknowledgment The brief critique given above about the pavement maintenance research conducted by pavement maintenance engineers of the Wisconsin Department of Transportation would not have been possible without the personal interests and project site inspections made by John W. Bugler, formerly a pavement maintenance engineer with of the New York State Department of Transportation. His interest and concern about that project over many years, his many examinations of the test pavements, and his reports of those examinations were invaluable in making an independent evaluation of the Wisconsin pavement maintenance research possible. His professional efforts in this respect were outstanding. Consequentially, the author of this book is pleased to have this opportunity to acknowledge John Bugler’s contribution to this work. That contribution will be of benefit not only to the members of the transportation profession in general but also and particularly to the highway travelers who will eventually be provided with a safer highway environment primarily because John Bugler took his pavement maintenance responsibilities so seriously.
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References 1. Shober, S. F., “The Effect of PCC Joint Sealing on Total Pavement Performance,” Fourth World Congress on Joint Sealants and Bearing Systems for Concrete Structures, American Concrete Institute, Sacramento, California, 1996 (preprint). 2. Shober, S. F., “The Great Unsealing: A Perspective on PCC Joint Sealing,” Transportation Research Record No. 1597, Transportation Research Board of the National Academies, Washington, D.C., 1997, pp. 22–33. 3. Burke, M. P. Jr., “The World’s Most Expensive Pavement Expansion Joints,” Ohio Transportation Engineering Conference Proceedings, The Ohio State University, Columbus, Ohio, 1972. 4. Burke, M. P. Jr., “Bridge Approach Pavements, Integral Bridges, and Cycle-Control Joints,” Transportation Research Record No. 1113, Transportation Research Board of the National Academies, Washington, D.C., 1987, pp. 54–65. 5. Richards, A. M., Causes, Measurements and Prevention of Pavement Forces Leading to Blow-Ups, The University of Akron, Akron, Ohio, 1976. 6. AASHTO. Standard Specifications for Highway Bridges, 17th edn, American Association of State Highway and Transportation Officials, Washington, D.C., 2002. 7. Milwaukee Journal Newspaper, July 7, 1970. 8. Buck, C. D., “Repair of Concrete Road Blow-Ups in Delaware,” Engineering News Record, Vol. 95, No. 11, 1925, pp. 432 and 433. 9. Burke, M. P. Jr., “Reducing Bridge Damage Caused by Pavement Forces,” Concrete International, American Concrete Institute, Farmington Hills, Michigan, January and February, 2004. 10. Smith, K. D., et al., “Pressure Relief and Other Joint Rehabilitation Techniques,” Report No. FHWA/RD-86/XXX, Federal Highway Administration, McLean, Virginia, 1987. 11. State Project No. 14668, Ohio Route 50, Joint Sealing Experiments (November 1996– 2001).
Appendix 2
Glossary
AASHTO: American Association of State Highway and Transportation Officials. Composite structure: An assembly of two or more different structural components integrated into a single functional whole. Cycle control joint: A transverse movable joint provided between bridge approach slabs and approach pavements to facilitate the longitudinal cyclic movement of bridge superstructures and attached approach slabs. DOT: Department of Transportation. Elementalism: The name given to the concept that reality is composed of discrete and independent objects that have been noticed and named. End diaphragm: A transverse reinforced concrete member used to integrate superstructure stringers and reinforced concrete deck slabs at abutments of semiintegral bridges. Expansion joint: Refer below to Movable joint and movable deck joint. FHWA: The Federal Highway Administration. It is an administrative agency of the US Department of Transportation. It is empowered by the US Congress to administer federal funds allocated for the design and construction of state and local highway projects. It encourages and provides funding for and supervision of transportation-related research projects intended to improve not only highway safety but also the materials and methods used in highway construction. G/P phenomenon: A temperature- and moisture-driven phenomenon whereby jointed rigid pavement periodically and progressively generates longitudinal pavement growth and/or pressure. 243
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Guide bearing: A movable bearing provided at abutments of skewed semi-integral bridges to facilitate differential longitudinal movement of superstructures with respect to abutments while providing lateral support for superstructures. Holism: The name given to the concept that reality is composed of a synergistically functioning whole. Integral abutment: An abutment that is constructed integrally with a bridge superstructure. Integral bridge: A single- or multiple-span continuous deck-type bridge without movable deck joints at the superstructure/abutment interface. It is generally supported by embankments and stub-type abutments on single rows of vertically oriented flexible piles, by flexible piers constructed compositely with the superstructure, or by semi-rigid piers with fixed and/or movable bearings. Movable deck joint: See Movable transverse deck joint. Movable joint: As bridge joints should be designed to accommodate anticipated multi-directional movements of bridge members due to various phenomena such as thermal changes, moisture changes, creep, elastic shortening, superimposed loadings, etc., it will be used in this book instead of the archaic misnomer “expansion joint.” Movable transverse deck joint: A transversely oriented movable joint in bridge superstructures intended to facilitate differential movement of superstructures or superstructure segments with respect to piers, abutments, or other superstructure segments. Pressure relief joint: A transversely oriented movable pavement joint (usually 1–4 ft. [0.3–1.2 m] wide and usually filled with compressible asphalt concrete) provided between jointed rigid pavement and bridge approach slabs to protect both pavements and bridges from the longitudinal pressures generated by the pavement G/P phenomenon. Semi-integral bridge: A single- or multiple-span, continuous, deck-type bridge without movable deck joints in its superstructure but with movable longitudinal joints between its superstructure and abutments. Abutments of such bridges should be rigidly supported. Piers can be flexible and constructed integrally with the superstructure, or rigid with fixed and/or movable bearings. Structure movement system: A complex unity of diverse components configured and designed to facilitate structure movements (rock, roll, slide, shear, flex, compress, consolidate, etc.) in response to applied loads and to material and environmental changes. TRB: The Transportation Research Board is one of six major divisions of the National Research Council. Its mission is to promote innovation and progress in transportation through research. In an objective and interdisciplinary setting, the Board facilitates the sharing of information on transportation practice and policy by researchers and practitioners, stimulates research and offers research management services that promote technical excellence, provides expert advice on transportation policy and programs, and disseminates research results broadly and encourages their implementation.
Appendix 3
Captions for Photographs
These photographs appear on the first page of each chapter of this book. Introduction: Twisp River Bridge, Twisp, Okanogan County, Washington State, 2001. This innovated semi-integral bridge is supported by field-spliced, prestressed, post-tensioned, high-performance concrete girders. With a spectacular single span of 197 ft. (60 m), it is probably the longest single span semi-integral bridge in the world. Chapter 1: SR 50, Happy Hollow Creek Bridge, Hickman County, Tennessee, 1996. This is probably the world’s longest integral bridge. Its overall length is 1,175 ft. (358 m). Chapter 2: SR 21, West Fork of Black River Bridge, Reynold County, Missouri. This nine-span, 765 ft. (233 m), prestressed, concrete integral bridge has a centerline of roadway radius 2865 ft. (873 m). Chapter 3: Rainbow Bridge National Monument. It spans a tributary of the Colorado River near the Utah–Arizona border. It has a span of 275 ft. (84 m) and a rise of 290 ft. (88 m). It is the world’s largest natural integral bridge. Chapter 4: Naibekoshinai River Bridge, Hokkaido, Japan, 1996. This is one of the first of two early integral bridges constructed in Japan. It has three continuous spans with an overall length of about 560 ft. (110 m). Chapter 5: SR 7, Teens Run Bridge, near Eureka, Ohio, 1938. This five-span, continuous, reinforced-concrete structure, with each of its integral stub-type 245
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Appendix 3
abutments supported by a single row of flexible piles, is thought to be the first integral bridge constructed in Ohio. It is probably the first such bridge constructed in the United States and possibly the world. It has an overall length of about 144 ft. (44 m). Chapter 6: DooDong Bridge, Ham Yang Co., South Kyung Province, South Korea, 2001. The original project plans for this bridge provided it with movable deck joints at piers and abutments. Those plans were revised (except for pier details) before construction to provide Korea with its first integral bridge. Chapter 7: Route 401, Prospect Avenue Bridge, Toronto, Ontario, Canada, 1995. This relatively new, steel box-beam integral bridge is about 490 ft. (150 m) long. Chapter 8: USR 23, SR 32 Bridge, Pike County, Ohio, 1996. This twin, heavily skewed, semi-integral bridge was provided with two accessible guide bearings at each abutment of both structures (see Figures 8.6 and 8.7). Chapter 9: USR I-90 B. N. Railroad bridge, Grant County, Washington State, 1966. This early semi-integral bridge performed well in simulated seismic tests in 1993 just before its removal. Chapter 10: SR 555, Muskingum River Bridge, Zanesville, Ohio, 1979. This is the first semi-integral bridge constructed in Ohio. It has three continuous spans with an overall length of 540 ft. (165 m). Abutment details are illustrated in Figure 1.8. Chapter 11: Price-Hillards, Scioto Darby Creek Road Bridge, Franklin County, Ohio, 1986. This is the first integral bridge with drilled-shaft piers constructed in Ohio. Appendix 1: A27 – Brockhampton Road Bridge, Hampshire, United Kingdom, 2001. This 215 ft. (65.5 m), three-span, continuous, steel-girder integral bridge is supported by both integral abutments and piers and cast-in-place concrete piles. Appendix 2: Route 401, Franklyn Boulevard Underpass, Ontario, Canada, 1990. The original, continuous precast, prestressed, concrete box-girder integral bridge was just recently widened using the same type of primary members. Appendix 3: SR 725, Sycamore Creek Bridge, Miami Township, Montgomery County Ohio, 1963. This was the first integral steel-beam bridge constructed in Ohio. The steel portions of this structure were cleaned and painted, and the original concrete fascias of the deck were sealed shortly before this 1999 photograph was taken.
Index
Bridges Ashtabula River Valley Viaduct, Ashtabula, Ohio, 71–74, 78, 106, 107 A 27 Brockhampton Road Bridge, Hampshire, United Kingdom, 215, 246 Broad Road Viaduct, Bedford, Ohio, 76 Brookpark Viaduct, Cleveland, Ohio, 74 Cuyahoga River Valley Bridge, Brecksville, Ohio, 76, 106–107, 115 Doodong Bridge, Ham Yang Co., South Kyung Sang Prov., South Korea, 81, 246 General US Grant Suspension Bridge, Portsmouth, Ohio, 212 Golden Gate Bridge, San Francisco, California, 193 Happy Hollow Creek Bridge, Hickman County, Tennessee, 1, 8, 43, 57, 118, 245 John F. Kennedy Memorial Bridge, Louisville, Kentucky, 23, 25–27, 29 Long Island Bridge, Kingsport, Tennessee, 6 Mianus River Bridge, Greenwich, Connecticut, 213 Naibekoshinai River Bridge, Hokkaido, Japan, 59, 71, 78, 245 Ohio Bridge No. GEA – 422 – 0057, Geauga County, Ohio, 197
Ohio Bridge No. HIG – 28 – 0280, Highland County, Ohio, 191, 192 Ohio Bridge No. WAY – 585 – 0859, Wayne County, Ohio, 194, 195 Old North Hill Viaduct, Akron, Ohio, 103–106, 115, 118 Old Third Street Viaduct, Cincinnati, Ohio, 23–25, 29 Patterson-Riverside Great Miami River Bridge, Dayton, Ohio, 4, 5 Pecos River Bridge, Carlsbad, New Mexico, 23, 27–29 Price-Hillards Scioto Darby Creek Road Bridge, Franklin County, Ohio, 246 Rainbow Bridge National Monument, Utah/Arizona Border, 41, 245 Route 401, Franklyn Boulevard Underpass, Ontario, Canada, 243, 246 Route 401, Prospect Avenue Bridge, Toronto, Canada, 99, 246 Salginatobel Bridge, Schiers, Switzerland, 109 Schoharie Creek Bridge, Montgomery County, New York State, 213 Silver Bridge, Gallipolis, Ohio, 213 SR 21 Barberton Reservoir Inlet Bridge, Akron, Ohio, 35, 36 SR 21 West Fork Black River Bridge, Reynold County, Missouri, 21, 245 SR 180 – USR 33 Bridge, Hocking County, Ohio, 91 SR 250 – 148th Avenue N. E. Bridge, King County, Washington State, 91, 92 SR 555 Muskingum River Bridge, Zanesville, Ohio, 137, 157, 246 247
248
Index
SR 725 Sycamore Creek Bridge, Miami Twp., Montgomery County, Ohio, 245, 246 SR 771 Big Branch Creek Bridge, Highland County, Ohio, 89–90 Stanley Avenue – B&O Railroad Bridge, Dayton, Ohio, 230, 231 Teens Run Bridge, Gallia County, Ohio, xii, 71–72, 75, 76–77, 78, 139, 245 Tocoma Narrows Bridge, Tocoma, Washington State, 193 TR 45 – CSXT Railroad Bridge, Pickaway County, Ohio, 44, 95 Twisp River Bridge, Twisp, Okanogan County, Washington State, 11, 245 USR 23 – SR 32 Bridge, Pike County, Ohio, 121, 129–131, 246 USR 52 Little Scioto River Bridge, Portsmouth, Ohio, 33, 34 USR 62 Yankee Creek Bridge, Trumbull County, Ohio, 82, 83 USR 422 McFarland Creek Bridge, Geauga County, Ohio, 197–199 USR I-35W Mississippi River Bridge, Minneapolis, Minnesota, 213 USR I-76 – East Market Street Bridge, Akron, Ohio, 166, 167 USR I-77 – SR 18 Bridge, Summit County, Ohio, 97 USR I-90 – B. N. Railroad Bridge, Grant County, Washington State, 139, 197, 202, 246 USR I-90 – 140th Street Bridge, Cleveland, Ohio, 232, 233 USR I-271 – Wilson Mills Road Bridge, Cleveland, Ohio, 37 USR I-480 Cuyahoga River Valley Bridge, Cleveland, Ohio, 177, 179
General AASHTO (American Association of State Highway and Transportation Officials), 22, 217, 243 AASHTO Standard Design Specifications for Highway Bridges, 37, 39, 112–113, 204, 217
abutment backfill. See backfill capped pile, 1, 2, 51, 198 continuity connection, 16, 48, 54, 62, 65 embankments. See embankments flexible, 19, 72, 75, 76 flexible supports, 114 integral. See bridges, integral non-integral, 7, 9, 169 pile cap, 97 pile foundations. See piles semi-integral. See bridges, semi-integral settlement, 2, 18, 60 stub-type, 2, 7, 42, 47, 52, 59, 69, 76, 82, 116, 169 wall-type, 7, 82, 166 wingwalls, 161 reinforcement, 9, 69, 117 turn-back, 12, 137, 151 American Iron and Steel Institute, 118 anchor bars, holes, 49–50 angle of internal friction, 62, 127 approach pavement, 170 asphalt (bituminous) concrete, 93 concrete, 28 growth. See G/P phenomenon jointed, 2, 21, 22, 23, 26, 55, 170 rigid, 6, 39, 55 approach slabs, 180 anchors, 2, 151 curbs, 69 cycle-control joints, 95, 133, 151, 244 compression seals, 96 curb inlets, 97 drainage troughs, 55, 97 fingerplates, 97, 162 pressure-relief joints, 45, 55, 56, 57, 117, 245 strip seals, 96 diagonal tie bars, 93, 116 full-width, 55, 94, 97, 102, 134 mechanical connectors, 54, 137 polyethylene sheets, 55, 88, 136 seats, 93 assumptions realistic, 99 simplifying, 65–67, 100, 115 awareness, lack of, contributing reasons economics, xii, 209, 212 habit, 209–210, 212,
Index
language, 210, 212 preoccupation, 207, 212 awareness of change, 186, 192–195, 212 of differences, 186, 196–197, 212 of reality, 185–186, 190, 208, 212, 213 of similarities, 197 of things, 186–192 backfill compressible, 170, 197 compression, 56, 62, 125 consolidation, 55, 63 erosion, 12, 55, 134 expansion, 56 frictional resistance, 126 granular, 62, 69 placement procedures, 137 shearing resistance, 137 well-drained, select granular, 12, 69, 117 beams, uplift. See buoyancy countermeasures bearings abutment, 113 anchor bars, 49–50 bolster, 23, 167, 177 compound, 168 elastomeric, 48, 94, 123, 133, 168, 170, 172, 173, 180, 181, 198–199, 204, 206 fixed, 25, 47, 177 guide, 93, 124, 125, 126, 129, 130–132, 144, 154, 181, 197, 244 accessible, 131, 197 replaceable, 197 movable, 2, 14, 22, 41, 42, 43, 44, 47, 49, 59, 65, 158, 159, 161, 169, 170, 173, 180, 181 rockers, 167 roller, 177, 178 blow-up Allen Road, Toronto Canada, 229 approach slabs, 216 pavement, 31–32, 35, 215, 223 records, 225–228 stone-block streets, 31, 228 bridge, cast-in-place concrete, 103, 150, 168 characteristics aesthetics, 109 durability, 109 economy, 109, 116
249
function, 109 safety, 116 collapsed, 46, 88 construction, foundations integral, 52, 60 procedures, 10, 53, 57, 68 stage, 46, 192 continuous, concrete slab, 71, 72, 74 end-jointed, 14, 22, 32, 35 integral, 7–8, 35, 48 multiple-span, 3, 60, 72, 75, 137, 216 prestressed box-beam, 5, 16, 71, 72, 191, 192, 198, 205 steel stringer-type, 74 superstructures, 19 bridge, composite concrete conversion techniques, 17 cost-effective, 2 deck-type, xii, 89, 94, 103, 112 deflections, 64, 87 durability, 183 functional, 183 foundation restraint, 10 foundations, old, 48 grade separation, 50, 107, 113 Inspector’s Training Manual, 37, 38 bridge, integral abutment, 2, 4, 11, 12, 19, 86, 118, 169, 206, 207, 244 aesthetics, 116 attributes broad span ratios, 50, 51 compressive resistant, xii, 230 cost-effective, 2 dry construction, 45 durable, 2, 43, 100, 116 load distribution, 113 pressure resistant, 22, 42 rapid construction. See Bridge, integral, construction safety, 116 simple design, 43–44 simple replacement, 51 simple widening, 51 concept, 93, 244 concrete, 7, 59 construction, 43, 53, 59 broad tolerances, 46, 47 embankments, 46 few parts, 27 no cofferdams, 46
250
Index
small excavations, 46 simple beam seats, 47 simple forms, 47 vertical piles, 46 cost-effective, 2, 42 integrity, 2, 43, 100 limitations alignment, xi application range, 52, 68 approach guard rail connections, 53 approach slabs required, 12, 55, 56, 88 buoyant. See buoyancy, countermeasures continuity required, 117 curvature, 57, 112, 116, 118 cycle-control joints. See approach slabs flexible abutments, 9, 53, 59, 182 length, 7–8, 11, 43, 52, 57, 69, 116 overburden depth, 5, 57 pile length, 13 pile stresses, 10, 13, 51–52, 139 settlement control, 64–65 skew, 13, 43, 57, 69, 76, 112, 116, 118 uplift. See buoyancy load capacity, 59 multiple-span continuous, 3, 43, 47, 59, 69, 216 pier. See piers precast prestressed, 1 prestressed concrete, 10, 16 reinforced concrete slab, 3, 16, 113, 116, 194 replacement, 89 restraint, longitudinal active earth pressure, 68 approach slab/subbase friction, 169 backfill compression, 56 bearing shear, 124 passive pressure, 11, 55, 59, 112 wingwall/backfill friction, 7 rolled steel beams, 3 bridge, semi-integral attributes aesthetics, 142 broad application range, 123 broad skew range, 91 compression resistant, xii, 124 durable, 140 earthquake resistant, 50, 124
jointless deck, 122, 132, 147, 152, 169, 239 length, 153 rigid foundations, 114, 121, 152, 196 concept, 121, 134, 140–142, 180, 205, 244 experience, 144 limitations alignment, 153 application range, 140 approach slabs, 136, 141, 153 buoyant, 153 continuity required, 153 cycle-control joints, 141, 153, 154, 197 lateral force control, 153 length, 153 restricted settlement, 152 rigid foundations, 132, 141, 153 representative details, 147 seismic research, 200 use, 142 bridge, settlement, 2 Bugler, John W., 234, 241 buoyancy, countermeasures counterweights, 67 drain holes, 132 floodwater clearance, 53 integral abutments, 86, 118, 197, 206, 207, 244 integral piers, 132 mechanical hold-down connections, 53, 88 vent holes, 53 cofferdams, 46 columns flexible, 73, 196 slender, 196 composite structure. See structure movement systems concrete closure placements, 86, 88, 97 crack sealers, 85, 87 curing blankets, 61, 84 diaphragms, 16 end diaphragms, 84, 85, 87, 89, 91, 95, 136, 180 finishing, machines, 84, 85 forms, 61 high performance, 85 high strength, 85
Index
placement, 16, 47 days, 54, 87, 88, 91 night placement, 85–86, 87 procedures, 84 rapid, 85 sequences, 84, 85 set-retarding admixtures, 85 water curing, continuous, 87 construction accelerated, 82 all-weather, 82 cast-in-place, 10 continuous, 69, 116 jointless, 44–45 procedures, 53 specifications. See AASHTO Standard Design Specifications for Highway Bridges stage, 89, 192, 194 continuity, connections abutments, 54, 61, 62, 88 cast-in-place, 10, 50, 86, 116 moments, 3, 61, 65 reinforcement, 16, 65, 69, 191 superstructure/abutment, 44, 48, 67, 86, superstructure/pier, 16, 44, 68 continuous, construction deck slab, 73, 75, 112 frames, 3, 9 highway bridges, xi, xii, xiii, 3, 74 multiple span bridges, 69, 216 contraction, 9, 10, 103, 107–108, 175 conversions, integral, 15, 17, 82 corrosion, 7 counterweights. See buoyancy cracking diagonal, bridge deck, 82, 97 early age deck slab, 82, 83–85, 86, 87, 97 flexural, deck slab, 9, 85 sealant, 23 transverse, bridge deck, 83, 84, 85, 113 creep. See stresses, secondary Cross, Hardy, 3, 99–100 cycle-control joints, 2, 55, 57, 95, 151, 243 debris, infiltration, roadway, compression resistant, 30, 93, 102, 221, 237, 240 deck, drainage curb inlets, 102 downspouts, 102
251
hinges, 17 horizontal conductors, 102 joints. See joints scuppers, 102 deck slab closure placements, 89, 90, 91 concrete placement procedures, 84, 86, 162 sequences, 84, 86, 112 speed, 112 machine finishing, 84, 85, 87 transverse cracking, 83, 84, 86, 87, 224 de-icing chemical deterioration, xii, 7, 8, 113, 122, 152 design intuition, 182 prudent judgment, 19 simplified assumptions, 62 design, specifications. See AASHTO Standard Design Specifications for Highway Bridges deterioration, environmental, 194 diaphragm concrete end, 141, 204 concrete placement, 135–136 transverse, end, 83 drainage, deck, 7, 102, 151 earthquake North Ridge, 147 resistance, 200 elastomeric compression seals, 7, 96, 133 erection devices bearings, 48, 50, 51, 122, 123, 124, 133, 145, 180, 181, 198–199, 203, 206–207 strips, 48–49, 206–207 joint seals, 7, 47, 96, 97, 124, 133, 181 membrane. See deck slab elementalism, 157, 159, 163–165, 166, 243 elementalistic, approach, 157, 159, 175 embankment benches, 63, 69, 117 consolidating, approach, 93–94, 116, 158 consolidation, 82, 94, 117, 129, 165, 170, 175, 182, 198 construction, 44, 53–54 erosion, 82, 97 mechanical stabilized, 169 placement procedure, 84, 137
252
Index
scour, 170 settlement, 165 side-slope drainage flumes, 97, 102, 134, 154 spill-around slopes, 63 stable, 169 waiting period, 69 end diaphragms concrete, 85, 180, 243 concrete placement, 87, 89, 135–136, 180 factors distribution, 65, 164 stiffness, 43, 65 fatigue design categories, 114 procedures, 114 specifications, 114 Federal Highway Administration, 14, 235 forces lateral, 112 longitudinal, 13, 31, 39, 64, 118, 124, 152, 162, 165 foundations, abutment flexibility, 72 flexible, end-bearing flexible piles, 74, 121, 181 flexible capped piles, 68, 75, 82, 197 rigid battered piles, 82, 196 bedrock, 75 drilled shafts, 121, 181, 196 pedestals on bedrock, 75, 82, 121, 122, 181, 196 semi-rigid, 12, 19 G/P generation factors concrete strength, 223 de-icing chemicals applications, 7, 16, 30, 77, 103, 219, 224 joint design and spacing, 223 joint spacing, 228, 237 pavement age, 16–17, 25, 28, 229–230 rainfall, 223 sealant maintenance, 224 sealant quality, 223 subgrade composition, 223 subgrade drainage, 223 temperature range, 54, 223 traffic volume, 31, 224 G/P phenomenon, xi, xii, 11, 21–39, 43, 45, 112, 123, 133, 215–242, 243
General Structures Committee, 157 guard rail connections, 53 Hindman, William S., 76–77 hinges, plastic. See piles holes drain. See buoyancy vent. See buoyancy holism, 157, 244 holistic, approach, 157 evaluation, 174 views, 159, 162, 163–165, 166, 167, 168, 180 view boundaries, 175, 176, 177 integral construction. See bridges, integral integrated superstructure system, 18–19, 166 interface abutment backfill, 170, 197 approach-slab/aggregate-base, 93 approach-slab/approach-pavement, 2, 53, 132, 133, 197 approach-slab/approach-sidewalk, 96 approach-slab/superstructure, 93 bridge/embankment, 50, 96 end diaphragm/backfill, 126, 129, 135, 151, 180 polystyrene/concrete, 20 superstructure/abutment, 2, 7, 17, 19, 23, 25, 32, 34, 35, 42, 43, 59, 82, 85, 152, 171, 180, 182, 215, 232 joint closed, 45 contraction sealed or unsealed, 240 spacing, 237 cycle-control. See approach slabs, 2 debris infiltration, 30–31, 233 elastomeric, seal, 7, 47 expansion, 8, 9, 73, 74, 106 fillers compressible, 133 polyethylene, 25 movable, deck, 2, 14, 22, 41, 42, 45, 59, 67, 71, 73, 82, 86, 94, 96, 103, 106, 107, 114, 122, 158, 159, 161, 162, 168, 171–172, 173, 177, 182, 215, 233, 239, 244 longitudinal, 2, 23, 82, 91, 132, 181 transverse, 1, 95 open, 109
Index
pavement expansion, 233, 239 pressure relief, 25, 26, 27, 29, 34, 35, 38, 39, 45, 56, 60, 96, 117, 134, 233, 235, 236, 239 saw-cut, 219 sealed, 7, 45, 221, 235 sliding plate, 7, 96, 162 transverse deck, 1 unsealed, 30, 221, 234–235 Land of No Special Computations, xiii, 12, 108, 109, 111, 115, 116, 118 loads dead, 60 horizontal, 68 lateral, 118 live distribution, 113 surcharge, 55 longitudinal, 118 ultimate capacity, 60 mechanical connectors, 88 modulus, elastic, 60, 94 moments continuity connection, 16, 61, 62 negative, 15, 61, 62 positive, 16, 50, 61, 62, 65 movement systems. See structure movement systems movements abnormal rotations, 167 differential, 86 horizontal, 93 longitudinal, 87 rotational, 87 National Bridge Inventory, 118 Naval facilities command, 70, 138 nouns apparition type, 210 ethereal type, 210 process type, 210 singular, 210–211 static type, 210 Odd Albert’s Method, 115 pavement approach blow-up, 31–32, 35, 215, 225, 235, 236
253
compressive stresses, 31, 225 contraction joints, transverse, 30, 219 expansion joints, 38, 96, 106, 133, 240 forces. See pressure growth. See G/P phenomenon restrained, 21, 37, 64 jointed concrete, 2, 22, 23, 31, 32, 35, 45, 60, 170 pressure, 6, 34, 45 pressure relief joints. See pressure relief joints pumping, 96 PCI manual, 197 PCI Precast/Prestressed Integral Bridges, 16, 197, 205 piers cap-and-column, 175, 188, 200 capped pile, 1, 51, 198 continuity connections, 43, 44, 47 fixed, 44, 68, 160 flexible capped pile, 68, 75 flexible integral, 2, 42, 43, 44 49 self-supporting, 2, 43, 49, 50, 59, 65, 68 semi-rigid, 2, 42, 65, 68 pile battered, 46, 68, 196 cap, connection reinforcement, 9, 44 capped piles. See piers cast-in-place, 10, 52 driving constraints, 199 elastic range, 52 flexible, 42, 59, 65, 69, 82, 116, 169, 197, 206 flexural resistance, 52, 63 flexural stresses, 9, 52 plastic hinges, 13, 52 prebored holes with granular material, 13, 52, 53, 63, 117 precast concrete, 52 prestressed reinforced concrete, 16, 52 single row, 8, 52 steel H, 8, 9, 13, 34, 52, 116 test research, 52 vertically driven, 2, 116, 196 weak axis, 116 polyethylene, sheets, 88, 136, 203 polystyrene, expanded, 94, 142, 145, 201, 204 pressure active, 128 distribution, 63
254
Index
generation curve, 31, 222, 233, 240 generation of, 6, 31, 237 pressure relief joints asphalt (bituminous) concrete, 56, 93, 239 polymer foam filled, 236 sleeper slabs, 56, 96 subbase drains, 56 problems elimination, 100, 101–102 ignore nonproblems, 100, 101–102 recognizing, 100–101 redefining, 100, 102–103 simplifying, 100, 103–110 solving, 100 reinforcement, negative moment, 62 research creep studies, 56, 62 half-scale model, 61 integral-bridge, 8 passive pressure, 56, 62 pile test, 52 seismic, 94, 200 shrinkage, xii, 16, 56, 62 soil/structure interaction, 154 restraint, foundation lateral, 123, 124 longitudinal, 123–124 rotational, 125 roads, interstate primary system, 43, 179 secondary system, 43 roadway shoulders curb inlets, 102 drainage, 95 erosion, 95 side-slope flumes, 154 subsidence, 94 underdrains, 97, 134 rock mechanics, techniques, 215, 222 rotation abnormal, 167 horizontal, 93, 129 superstructure, 197 seals deck joint, 67, 82 elastomeric compression, 7 elastomeric joint, 97, 159 elastomeric sheet, 133 joint, 67, 82
secondary effects. See stresses settlement differential, 174 post-construction, 175 vertical, 181 shrinkage, xii, 9, 30, 44, 51, 60–61, 87, 103, 107–108, 175, 176 skew, xii, 43, 76, 91, 112, 118, 125, 130, 144, 165, 196 skew limitations, 5, 11, 43, 150 snow plows, 67 span continuous, 15 simply supported, 14, 89 width ratio, 113 stage reconstruction, 89 strength fatigue, 90 ultimate, 90 stresses primary buoyancy, xii dead load, 51, 60, 66, 67, 68, 85 earthquakes, xii, 50, 67, 124, 199, 217 flexural, 9 live load, 51, 55, 60, 66, 67, 68, 75, 112 pavement pressure, 7, 16–17, 31, 34, 38, 43, 112, 218–224 secondary creep, 44, 51, 60, 61–62, 65, 66, 67, 68, 176 passive pressure, xii, 11, 44, 52, 55, 57, 60, 61, 65, 66, 68, 139, 180 settlement, xii, 60 shrinkage, xii, 10, 16, 44, 51, 60–61, 66, 67, 68, 75, 87, 107–108, 175 stream flow, 68, 113 temperature, 87 thermal gradients, xii, 52, 60, 61, 65, 67, 68, 75, 84, 176 wind, 68, 113 stringer support bolts, 88 structure durability, 106 integrity, 106 movement subsystems movement systems, xii, 1–2, 93, 97, 157, 159, 161, 162, 165, 168–171, 172, 173, 175, 176, 179, 180, 182, 183, 197, 198, 200, 244 movement systems, 140, 144
Index
primary, 170 secondary, 170 tertiary, 170 structures continuous, 168 grade separation, 50 Study Tour of North America, 8 subsoil consolidation and translation, 69, 158 stability, 53, 57 stable, 50 surcharged, 69, 116–117, 158, 175, 179 substructure, 170 capped pile, 200 flexibility, 2, 51 superstructure, 197 superstructure restraint, longitudinal, 123–124 active earth pressure, 68, 124 approach-slab/subbase friction, 124, 127, 129, 169 backfill compression, 56, 62, 125 bearing shear, 124 passive pressure, 11, 55, 60, 124, 125–126, 127, 128, 180 wingwall/backfill friction, 7, 124 temperature ambient, 54, 93, 160, 219 changes, 29 levels, 65
255
movement coefficient, thermal. See stresses range, 54 thermal gradients, xii, 65, 176 traffic maintained, 89, 193, 194 vehicular, 31, 35, 50, 55, 166, 167, 224 Transportation Research Board (TRB), 157, 244 TRB Structure Movement Systems Subcommittee, 158 uplift. See integral and semi-integral bridge limitations buoyancy. See buoyancy deck placement, 54 mechanical hold-down connections, 53, 88 vehicular traffic. See traffic views elementalistic. See elementalism holistic. See holism multidimensional, 179 welder pre-qualification tests, 3 welding, butt beams, 3 field, 3 fillet, moment plates, 3 splices, 3