Bridge Engineering

Bridge Engineering

Bridge Engineering Design, Rehabilitation, and Maintenance of Modern Highway Bridges Jim J. Zhao, P.E. President Frederick Engineering Consultants, LLC

Demetrios E. Tonias, P.E. President HMC Group Ltd.

Third Edition

McGraw-Hill, Inc. New York San Francisco Washington, D.C. Auckland Bogota´ Caracas Lisbon London Madrid Mexico City Milan Montreal New Delhi San Juan Singapore Sydney Tokyo Toronto 

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iv

BRIDGE ENGINEERING

Library of Congress Cataloging-in-Publication Data Tonias, Demetrios E. Bridge engineering : design, rehabilitation, and maintenance of modern highway bridges / Demetrios E. Tonias. p. cm. Includes bibliographical references and index. ISBN 0-07-065073-X (alk. paper) 1. Bridges — Design and construction. 2. Bridges — Maintenance and repair. I. Title. TG300.T66 1994 624'.2 — dc20 95-12958 CIP

Copyright © 1995 by McGraw-Hill, Inc. All rights reserved. Printed in the United States of America. Except as permitted under the United States Copyright Act of 1976, no part of this publication may be reproduced or distributed in any form or by any means, or stored in a data base or retrieval system, without the prior written permission of the publisher. 1 2 3 4 5 6 7 8 9 0

KPT/KPT 9 0 9 8 7 6 5 4

ISBN 0-07-065073-X The sponsoring editor for this book was Larry S. Hager, the editing supervisor was David E. Fogarty, and the production supervisor was Donald Schmidt. This book was designed and set by Demetrios E. Tonias. Printed and bound by Arcata Graphics/Kingsport.

Printed on acid-free paper.

Information contained in this work has been obtained by McGraw-Hill, Inc., from sources believed to be reliable. However, neither McGraw-Hill nor its author guarantees the accuracy or completeness of any information published herein and neither McGraw-Hill nor its author shall be responsible for any errors, omissions, or damages arising out of the use of this information. This work is published with the understanding that McGraw-Hill and its author are supplying information but are not attempting to render engineering or other professional services. If such services are required, the assistance of an appropriate professional should be sought.

v

Contents

Preface Section 1

xxi

The Structure

1

1 . 1 USE AND FUNCTIONALITY 1.1.1 Terminology and Nomenclature - 4 1. Superstructure - 4 2. Substructure - 6 3. Appurtenances and Site Related Features - 9 4. Miscellaneous Terms - 11 1.1.2 Structure Types and Applications - 12 1. Slab-on-Stringer - 13 2. One-Way Slab - 15 3. Steel and Concrete Box Girder - 15 4. Cable-Stayed - 16 5. Suspension - 16 6. Steel and Concrete Arch - 17 7. Truss - 17

3

1 . 2 ORIGINS OF THE MODERN HIGHWAY BRIDGE

17

1 . 3 BRIDGE DESIGNERS AND THEIR PROJECTS

20

1 . 4 THE BRIDGE ENGINEERING LEXICON

22

REFERENCES

Section 2

Project Inception

38 41

2 . 1 PROJECT FUNDING 2.1.1 User Fees - 42 2.1.2 Nonuser Fees - 43 2.1.3 Special Benefit Fees - 43 2.1.4 Private Financing - 43 2.1.5 Debt Financing - 44 2.1.6 Conclusions - 44

41

2 . 2 TYPES OF DESIGN STANDARDS 2.2.1 General Specifications - 45 2.2.2 Material-Related Design Codes - 46 1. Steel - 46 2. Concrete - 46 3. Timber - 47

45

viii BRIDGE ENGINEERING

Contents from 2.2.3 Use of Design Standards to 2.8 Conclusions

2.2.3 2 . 3 SITE 2.3.1 2.3.2 2.3.3 2.3.4

2.3.5

2.3.6

2.3.7

2.3.8 2 . 4 SITE 2.4.1 2.4.2 2.4.3

Use of Design Standards - 47 INSPECTION The Qualifications of Inspectors - 50 The Design Inspection - 50 Recording the Inspection - 51 Rating Substructure Elements - 52 1. Joints - 53 2. Bearings, Bridge Seats, and Pedestals - 53 3. Concrete Elements - 55 4. Steel Elements - 56 5. Timber Elements - 56 6. Embankment - 56 Rating Superstructure Elements - 57 1. Deck and Wearing Surface - 57 2. Primary and Secondary Members - 58 Rating Appurtenance and Site-Related Elements - 59 1. Railing - 59 2. Drainage Systems - 60 3. Utilities - 60 4. Lighting and Signing - 61 Inspecting for Scour - 61 1. The Channel - 61 2. The Substructure - 63 Conclusions - 63

49

SURVEY Topography - 64 Planimetry - 66 Structure Features - 66

64

2 . 5 PHYSICAL TESTING 2.5.1 Coring - 67 2.5.2 Delamination Testing - 68 2.5.3 Testing for Cover - 68 2.5.4 Measuring Steel Thickness - 68 2.5.5 Detecting Fatigue Cracks - 69

67

2 . 6 THE INSPECTION TEAM

69

2 . 7 AS-BUILT PLANS AND OTHER RECORD DATA 2.7.1 Supplementing As-Built Plans - 71 1. Guard Railing - 72 2. Drainage Facilities - 72 3. Traffic Barriers - 72 4. Miscellaneous Elements - 72 2.7.2 Other Sources - 73

71

2 . 8 CONCLUSIONS

73

CONTENTS

Contents from Section 2 References to 3.4.3 Compression Joint Seals

REFERENCES

Section 3

The Superstructure

74 77

3 . 1 SUPERSTRUCTURE TYPES 3.1.1 Steel Superstructures - 78 1. Rolled Beam - 79 2. Rolled Beam with Cover Plate - 79 3. Plate Girder - 79 4. Box Girder - 79 5. Steel Rigid Strut Frame - 80 6. Large Structures - 80 3.1.2 Concrete Superstructures - 80 1. Prestressed Concrete Girder - 80 2. Concrete Box Girder - 82 3. Concrete Slab - 83 4. Adjacent Prestressed Slab - 84 5. Concrete Rigid Frame - 84 6. Concrete Strut Frame - 84 7. Concrete Arch - 84 3.1.3 Timber Superstructures - 84 1. Glulam Timber - 84 2. Stressed-Laminated Timber Deck - 85 3. Trestle - 85 4. Truss - 85 3.1.4 Secondary Members - 86 1. Diaphragms - 86 2. Lateral Bracing - 88 3. Portal and Sway Bracing - 89

77

3 . 2 DECK TYPES 3.2.1 Noncomposite and Composite Decks - 89 3.2.2 Cast-in-Place Concrete Slab - 90 3.2.3 Precast, Prestressed Concrete Panels - 90 3.2.4 Steel Orthotropic Plate - 90 3.2.5 Steel Grid - 91 3.2.6 Timber - 92 3.2.7 Corrugated Metal - 92 3.2.8 Fiber Reinforced Polymer (FRP) - 92

89

3 . 3 WEARING SURFACE TYPES 3.3.1 Asphalt Concrete - 92 3.3.2 Polymer Modified Concrete - 93 3.3.3 High Performance Concrete - 93 3.3.4 Integrated Wearing Surface - 93

92

3 . 4 DECK JOINT TYPES 3.4.1 Open and Sealed Joints - 94 3.4.2 Filled Joints - 95

94

ix

x

BRIDGE ENGINEERING

Contents from 3.4.4 Strip Seal Joints to 3.7.4 Axial Force

3.4.3 3.4.4 3.4.5 3.4.6 3.4.7 3.4.8

Compression Seal Joints - 95 Strip Seal Joints - 96 Modular Joints - 96 Finger Plate Joints - 98 Sliding Plate Joints - 99 Conclusions - 99

3 . 5 DESIGN LOADS 3.5.1 Background and History - 100 3.5.2 Permanent Loads - 101 1. Dead Load - 101 2. Superimposed Dead Load - 102 3. Pressures - 103 3.5.3 Temporary Loads - 103 1. Vehicle Live Load - 103 2. Pedestrain Load - 105 3. Earthquake Loading - 106 4. Wind Loading - 112 5. Channel Forces - 114 6. Braking Force - 117 7. Centrifugal Forces - 117 8. Dynamic Load Allowance - 117 9. Construction Loads - 118 3.5.4 Deformation and Response Loads - 118 1. Shrinkage - 118 2. Creep - 119 3. Settlement - 120 4. Uplift - 120 5. Thermal Movement - 121 3.5.5 Group Loading Combinations - 122 1. AASHTO Standard Specifications - 122 2. AASHTO LRFD Specifications - 122

100

3 . 6 DESIGN METHODS 3.6.1 Working Stress Design - 126 3.6.2 Limit States Design - 128 3.6.3 Background and History - 129 3.6.4 The Many Names of Working Stress and Limit States - 131 1. Allowable Stress Design - 131 2. Service Load Design - 131 3. Load Factor Design - 131 4. Strength Design - 131 5. Ultimate Strength - 132 6. Load and Resistance Factor Design - 132

125

3 . 7 INTERNAL FORCES 3.7.1 Bending Force - 132 3.7.2 Shear Force - 133 3.7.3 Torsional Force - 133 3.7.4 Axial Force - 134

132

CONTENTS

Contents from 3.8 Load Distribution to 3.10.7 Shear Connector Design

3 . 8 LOAD DISTRIBUTION 3.8.1 How Loads Are Distributed - 135 3.8.2 Different Types of Load Distribution - 138 1. Interior Longitudinal Members - 138 2. Exterior Longitudinal Members - 138 3. Transverse Members - 139 4. Adjacent Concrete Slabs (or Box Beams) - 139 5. Other Multibeam Decks - 141 6. Slab-Type Bridges - 142 3.8.3 Conclusions - 142

134

3 . 9 CONCRETE DECK SLABS 3.9.1 Effective Slab Strip - 145 3.9.2 Calculation of Bending Moment - 146 3.9.3 Distribution Reinforcement - 149 3.9.4 Minimum Slab Thickness - 150 3.9.5 Empirical Design Method - 150 3.9.6 Slab Reinforcement Details - 152 3.9.7 Construction, Rehabilitation, and Maintenance - 153 1. Increased Slab Thickness and Cover - 154 2. Coated Reinforcement - 154 3. Waterproofing Membrane - 155 4. Drainage - 156 5. Snow and Ice Removal - 158 6. Patching - 159 7. Sealing - 160 8. Cathodic Protection - 161 9. Chloride Extraction - 162 10. Re-alkalization - 163 3.9.8 Conclusions - 163

143

3.10 3.10.1 3.10.2 3.10.3 3.10.4 3.10.5 3.10.6

164

3.10.7

COMPOSITE STEEL MEMBERS Composite Action - 164 Shored and Unshored Construction - 167 Effective Flange Width - 167 The Transformed Section - 169 Effects of Creep - 170 Choosing a Girder Section - 170 1. Compute Design Moments and Shear Forces - 170 2. Total Factored Moment and Shear Forces - 173 3. Choosing a Section - 174 4. Composite Section in Positive Flexure - 174 5. Composite Section in Negative Flexure and Non-Composite Sections - 180 6. Shaer Resistance of I-Sections - 185 7. Web Bending-Buckling - 187 8. Conclusions - 190 Shear Connector Design - 190 1. Fatigue - 190

xi

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BRIDGE ENGINEERING

Contents from 3.10.8 Cover Plates to 3.12.4 Influence Lines

2. Additional Geometric Constraints - 194 3. Effect of Stay-in-Place Forms - 195 4. Strength Limit State - 196 3.10.8 Bridge Fatigue - 202 1. Linear-Elastic Fracture Mechanics - 203 2. Stress-Life Method - 204 3. AASHTO Method - 206 4. Fatigue-Prone Details - 211 3.10.9 Deflections - 212 3.10.10 Camber - 214 3.11 3.11.1 3.11.2

3.11.3

3.11.4 3.12 3.12.1 3.12.2 3.12.3

3.12.4

PLATE GIRDER DESIGN Hybrid Girders - 217 Elements of a Plate Girder - 217 1. Flange Plate Thickness - 217 2. Flange Plate Economy - 218 3. Web Thickness - 218 4. Web Plate Economy - 219 5. Transverse Intermediate Stiffeners - 219 6. Transverse Intermediate Stiffener Economy - 224 7. Bearing Stiffeners - 225 8. Longitudinal Stiffeners - 226 9. Longitudinal Stiffener Economy - 228 10. Miscellaneous Economy Issues - 229 Lateral Bracing for Plate Girders - 230 1. Where Bracing is Located - 230 2. Bracing as a Function of Span Length - 231 3. Placement and Types of Lateral Bracing - 231 4. Eliminating Lateral Bracing - 231 5. Economy of Lateral Bracing - 232 Cross-Frames for Plate Girders - 232

216

CONTINUOUS BEAMS Advantages of Continuous Beams - 233 Rolled Sections as Continuous Beams - 234 Moment Distribution - 235 1. Overview - 235 2. Fixed End Moments - 235 3. Relative Beam Stiffness - 236 4. Fixity Factor - 236 5. Stiffness Factor - 237 6. Distribution Factor - 237 7. Carry Over Factor - 237 8. Method Synopsis - 237 Influence Lines - 242 1. General Moment Support Equation - 243 2. Unit Loads - 244 3. Influence Data at Intermediate Points - 245 4. Predefined Tables - 247

233

CONTENTS xiii

Contents from 3.12.5 Alternate Method for Analysis of Continuous Beams to 3.13.3. Weathering Steel

3.12.5 3.12.6

3.12.7 3.12.8

3.12.9 3.13 3.13.1

3.13.2

3.13.3

3.13.4

3.13.5 3.14 3.14.1

5. Using Influence Lines - 248 6. Area Under an Influence Line - 250 7. Conclusions - 253 Alternate Method for Analysis of Continuous Beams - 254 Live Load on Continuous Beam Structures - 263 1. Computing Moment Using Influence Lines - 264 2. Special Load Points - 266 3. Shear Forces - 266 Composite Section in Negative Bending - 267 Girder Splices - 268 1. Required Strength - 268 2. Welded Splices - 269 3. Bolted Splices - 270 4. Bolted Web Splices - 274 5. Bolted Flange Splices - 276 Pin and Hanger Assemblies - 278 PROTECTING STEEL SUPERSTRUCTURES Protective Coating Systems - 280 1. Background and History - 281 2. The Nature of Steel Corrosion - 282 3. Inhibitive Primers - 284 4. Sacrificial Primers - 286 5. Barrier Coatings - 286 6. Coating Applications - 287 7. Surface Preparation - 288 8. Overcoating - 294 9. Micaceous Iron Oxide (MIO) Coatings - 295 10. Conclusions - 296 Containment and Disposal of Paint Waste - 298 1. Background and History - 298 2. Containment Devices - 300 3. Recycling Abrasives - 304 4. Disposal Methods - 305 5. Conclusions - 307 Weathering Steel - 308 1. Background and History - 308 2. Material Properties of Weathering Steel - 309 3. Environmental Considerations - 309 4. Maintenance of Weathering Steel - 311 5. Inspection of Weathering Steel - 311 6. Rehabilitation of Weathering Steel - 312 7. Conclusions - 313 Galvanizing - 313 1. Overview - 314 2. Benefits and Drawbacks - 314 Conclusions - 315

280

LOAD RATING Inventory and Operating Ratings - 316

315

xiv

BRIDGE ENGINEERING

Contents from 3.13.4 Galvanizing to 3.16.2 Deterioration of Prestressed Concrete

3.14.2 3.14.3 3.14.4

3.14.5 3.14.6

3.15 3.15.1

3.15.2

3.15.3 3.15.4

3.15.5 3.15.6 3.16 3.16.1 3.16.2

3.16.3 3.16.4

Field Measurements and Inspection - 317 Loading the Structure - 318 Working Stress Method - 318 1. Steel and Wrought Iron - 319 2. Conventionally Reinforced and Prestressed Concrete - 320 3. Masonry - 321 4. Timber - 321 Load Factor Evaluation - 322 Load and Resistance Factor Method - 323 1. Overview - 323 2. Rating Procedures - 324 3. Fatigue Life Evaluation - 328 4. The Concept of Safe Evaluation - 330 5. Conclusions - 331 PRESTRESSED CONCRETE Overview of Prestressed Concrete - 331 1. Pretensioned Beams - 332 2. Posttensioned Beams - 333 3. Application of Pre- and Posttensioned Concrete - 334 4. Prestressing Steel - 334 5. Concrete for Prestressing - 335 Composite Beams - 336 1. Advantages - 336 2. Effective Flange Width - 336 3. Horizontal Shear - 336 Required Prestress Force - 340 Loss of Prestress - 346 1. Elastic Shortening - 346 2. Friction - 348 3. Anchorage Set - 350 4. Time Dependent Losses - 350 5. Total Loss - 354 Allowable Stresses - 354 Flexural Strength - 355

331

PRESTRESSED CONCRETE MAINTENANCE Overview - 359 Deterioration of Prestressed Concrete - 360 1. Cracking - 362 2. Other Forms of Concrete Problems - 362 3. Deterioration of Prestressing Steel - 364 Inspection of Prestressed Concrete - 365 Rehabilitation of Prestressed Concrete - 366 1. Patching - 368 2. Permanent Formwork - 369 3. Crack Injection - 369 4. Sealers - 370 5. Strengthening - 371 6. Conclusions - 372

358

CONTENTS

Contents from 3.16.3 Inspection of Prestressed Concrete to 4.1.8 Rehabilitation and Maintenance

REFERENCES

Section 4

372

The Substructure

379

4 . 1 ABUTMENTS 4.1.1 Types of Abutments - 380 1. Gravity Abutment - 381 2. Cantilever Abutment - 381 3. Full Height Abutment - 382 4. Stub Abutment - 382 5. Semi-Stub Abutment - 382 6. U Abutment - 382 7. Counterfort Abutment - 382 8. Spill-through Abutment - 383 9. Pile Bent Abutment - 383 10. MSE Systems - 384 4.1.2 Coulomb Earth Pressure Theory - 385 4.1.3 Abutment Foundation Design - 390 1. Loading - 392 2. Spread Footings - 393 3. Foundations on Piles - 396 4. Foundations on Drilled Shafts - 398 4.1.4 Abutment Stem - 400 4.1.5 Wingwalls - 400 4.1.6 Other Related Foundation Topics - 402 4.1.7 Mononobe - Okabe Analysis - 402 1. Background - 403 2. Horizontal and Vertical Seismic Coefficients - 404 3. Basic Assumption - 406 4. Active Earth Pressure - 406 5. Applying Active Earth Pressure - 408 6. Caveats - 410 7. Superstructure Loads - 410 4.1.8 Rehabilitation and Maintenance - 410 1. Cracking - 411 2. Surface Deterioration - 412 3. Stability Problems - 413 4. Bridge Seat Deterioration - 414 5. Sheet Piling Abutments - 416 6. Stone Masonry Abutments - 416 7. MSE Systems - 417 8. Footings - 418 9. Piles - 418

380

4 . 2 PIERS 4.2.1 Types of Piers - 421 1. Hammerhead - 422 2. Column Bent - 423

420

xv

Contents from 4.2 Piers to 5.1.2 Maintenance of Traffic

4.2.2 4.2.3 4.2.4

4.2.5 4.2.6

3. Pile Bent - 423 4. Solid Wall - 423 5. Integral - 424 6. Single Column - 424 Behavior and Loading of Piers - 425 Design Criteria - 425 Design of Compression Members - 428 1. Design Considerations - 429 2. Slenderness Effects - 430 3. Interaction Diagrams - 436 4. Limits of Reinforcement - 439 Rehabilitation and Maintenance - 441 Scour - 442 1. Overview - 442 2. Rehabilitation and Maintenance - 444 3. Replacement of Material - 445 4. Changing the Structure - 446 5. Replacing the Structure - 446

4 . 3 BEARINGS 4.3.1 Forces Acting on a Bearing - 447 4.3.2 Movement of Bearings - 449 4.3.3 Types of Bearings - 450 1. Rocker Bearings - 450 2. Roller Bearings - 451 3. Sliding Plate Bearings - 452 4. Pot Bearings - 452 5. Spherical Bearings - 453 6. Elastomeric Bearings - 453 7. Lead Rubber Bearings - 455 4.3.4 Rehabilitation and Maintenance - 456 REFERENCES

Section 5

Implementation & Management

447

457 459

5 . 1 THE HIGHWAY 5.1.1 Design Elements of a Highway - 460 1. Horizontal Alignment - 461 2. Vertical Alignment - 463 3. Stopping Sight Distance - 465 4. Roadway Width - 469 5.1.2. Maintenance of Traffic - 471

460

5 . 2 CONTRACT DOCUMENTS 5.2.1 Design Submissions - 474 1. Alternative Study - 474 2. Preliminary Submission - 475 3. Advanced Detail Submission - 476

473

CONTENTS

Contents from 5.2 Contract Documents to About the Authors

5.2.2

5.2.3

4. Final Submission - 477 Computer Aided Design and Drafting - 477 1. File Organization - 478 2. Geometric Source Files - 480 3. The Forgotten D in CADD - 480 4. Graphic Standards and Quality Control - 481 Conclusions - 482

5 . 3 BRIDGE MANAGEMENT SYSTEMS 5.3.1 Background and History - 484 5.3.2 Inventory Database - 485 5.3.3 Maintenance Database - 486 5.3.4 Project and Network Level Analysis - 486 5.3.5 Predicting the Condition of Bridges - 487 5.3.6 Miscellaneous Decision Assisting Criteria - 488 5.3.7 Costing Models - 488 5.3.8 Optimization Models - 489 5.3.9 Building the Database - 489 5.3.10 Managing Small and Large Structures - 490 5.3.11 Current Bridge Management Systems - 491 5.3.12 BMS Link to Design of Bridges - 491 5.3.13 BMS Link to Pavement Management Systems - 494 5.3.14 GIS and Imaging Technologies - 494

483

REFERENCES

495

APPENDIX

497

ACKNOWLEDGMENTS

499

ILLUSTRATION CREDITS

500

INDEX

502

ABOUT THE AUTHORS

509

Design Examples Section 3

The Superstructure

3.1

DESIGN OF REINFORCED CONCRETE DECK SLAB - STRIP METHOD

143

3.2

DESIGN OF COMPOSITE INTERIOR STEEL STRINGER

173

3.3

FATIGUE CHECK FOR A COMPOSITE STEEL STRINGER BRIDGE

203

3.4

INFLUENCE LINES FOR A THREE SPAN CONTINUOUS BEAM STRUCTURE

245

3.5

DESIGN OF TWO SPAN CONTINUOUS PLATE GIRDER BRIDGE

257

3.6

DESIGN OF PRESTRESSED CONCRETE I GIRDER BRIDGE

339

Section 4

The Substructure

4.1

DESIGN OF STUB ABUTMENT UNDER SEISMIC LOADING

383

4.2

ANALYSIS OF COLUMN BENT PIER UNDER SEISMIC LOADING

427

Section 5 5.1

Implementation & Management

CLEARANCE FOR A BRIDGE CROSSING AN UNDERPASS HIGHWAY

465

Design Perspectives A PREDATORY ATTITUDE?

21

IS PRIVATIZATION AN ANSWER?

43

WHO SHOULD INSPECT WHAT AND WHEN?

53

LIMIT STATES DESIGN - CONCRETE FIRST, STEEL FOLLOWED

128

AASHTO LOAD DISTRIBUTION: IS IT TOO CONSERVATIVE?

135

IS LEAD BRIDGE PAINT HAZARDOUS?

306

WEATHERING STEEL ENVIRONMENTS: THIS ONE'S JUST RIGHT.

310

STEEL VS. CONCRETE: WHICH ONE IS BETTER FOR BRIDGES?

340

Preface

T

he third edition of Bridge Engineering preserves most of the text and style of the previous ones. At the same time it presents a number of significant changes and additions. A book of this nature is an ever evolving project. During the time when this book was first written there had been a major change in the bridge design methods. Allowable stress design (ASD), and to some less extend, load factor design (LFD), dominated bridge engineering profession 17 years ago in this county. The Bridge Engineering saw a transition towards the load and resistance factor design (LRFD) when the second edition of the book was prepared. Today we have completed the transition of implementing LRFD as a uniformed design method. One thing we can be certain is that bridge engineering, whether the design theory or practice, will continue to advance in the years to come. As a result of implementing LRFD method, almost every section has been amended in some way and many have been expanded or substantially rewritten for the third edition. Also new to this edition are topics related to bridge load rating and fatigue life evaluation, which are essential part of bridge evaluation, maintenance, and management. Due to the advance of bridge design theory and construction materials, the improved design details accumulated from thousands of bridge designers and inspectors, the implementation of bridge inspection program, and bridge management system, we can now design bridges that last a lot longer with better safety and performance than the bridges built 50 years ago. This trend will certainly continue, with the help of bridge professionals like you. The third edition will not only introduce the theory and philosophy of bridge design to the young engineers but also present the complete tasks of bridge design, maintenance, inspection, rehabilitation, and management. I hope to enlist talents and new enthusiasm in working towards improving our aging transportation infrastructures. Our nation’s future economy and growth depend on newer and more reliable bridges in the transportation system.

Jim J. Zhao, P.E. Germantown, Maryland June, 2011

Preface to the First Edition

H

ighway bridges dot our landscape by the hundreds of thousands. We pass over and under them, paying no more attention to these structures than we would a tree or a hill. Indeed, the highway bridge has become part of our environment. From an historical perspective, the modern highway bridge was born in the depression years of the 1930's, came of age in the 1950's to 1970's, and is entering its golden years in the 1980's and 1990's. These structures have performed so well, they have been so durable, that most of us, engineers or not, tend to take the highway bridge for granted. We simply cannot envision a time when the life of these structures will reach the stage when they will no longer be so durable; when we will no longer be able to take the highway bridge for granted. We have, however, reached that time. The majority of bridges in our infrastructure were constructed in an era when the growth of our transportation networks was less of an expansion and more of an explosion. The engineers of this era were faced with the daunting task of designing and erecting structures at a pace that many engineers in the present, litigiously active, society have difficulty imagining. Because those individuals charged with the design and maintenance of these bridges did such a good job, the work of today's bridge engineers is tightly interwoven with those of their predecessors. Old bridges don't die or fade away; they deteriorate. The concrete spalls, the steel corrodes, the piers settle. Still, traffic passes over them. The snow plows come and the deicing agents spray against exposed concrete surfaces causing an electrochemical reaction that accelerates the deterioration of concrete. And still the traffic comes. The trucking industry, as much a beneficiary of the highway bridge as any other industry, pushes the design of structures to the outside of the envelope. Taller trailers barely squeak through minimum vertical clearances, heavier trucks test the load-carrying capacity of primary members. Through it all, the traffic still comes and, remarkably, the bridges still stand. How and why these highway bridges perform in such a remarkable fashion is what this book is about. Civil engineering, by definition, is a diverse, multifaceted profession. As civil engineering projects go, the design, rehabilitation, and maintenance of modern highway bridges requires the incorporation of just about every discipline in the civil engineer's repertoire. In this respect, integration, rather than specialization, is the key to the performance of a highway bridge.

T

he majority of bridges in our infrastructure were constructed in an era when the growth of our transportation networks was less of an expansion and more of an explosion.

xxii BRIDGE ENGINEERING

T

he reader, when using this text, should always keep in mind that this book is about bridge engineering; a subject which is much broader than bridge design alone.

Bridge Engineering Encompasses More Than Design How the Text Is Or ganized Design, Rehabilitation, and Maintenance Discussed Concur rently

There are many ways to write a book about highway bridges. The reader, when using this text, should always keep in mind that this book is about bridge engineering, a subject which is much broader than bridge design alone. In the past, it may have been possible for designers to ignore the important subjects of maintenance and rehabilitation when designing bridges. Today, however, there is a heightened awareness of the important roles these subjects play, even in the design of a completely new structure. Engineers are also increasingly being called upon to retrofit and strengthen existing structures which still can offer several years, if not decades, of additional service. This text is intended to serve as an overview of the bridge engineering process: from the origins of a bridge project through its design and the eventual maintenance and rehabilitation of a structure. Due to the wide variety of structure types currently being used, it would be impossible for any single volume to cover each specific type of highway bridge in intimate detail. An attempt has been made, however, to provide a description of all of the major forms of highway bridges used, with an emphasis placed on the types of structures which are most prevalent. The book is divided into five major sections which provide an examination of o o o o o

The structure as a whole How a bridge project begins Superstructure elements Substructure elements The implementation and management of a bridge in a highway network

The reader will notice that there is no specific section for design, rehabilitation, or maintenance. All three subjects are discussed concurrently for any given topic. For example, the design of a concrete deck is followed immediately by a discussion of rehabilitation and maintenance techniques. The material is organized in such a fashion, in part, because it is functional and beneficial to the reader. The organization of the material, however, is also meant to serve as a symbol of the importance of integrating these three project phases. One cannot design a structure in today's environment without planning for its future maintenance. Similarly, it is impossible to maintain a bridge without understanding the nature of its design. The rehabilitation design of a structure offers a whole new set of circumstances which confront an engineer. All of these subjects play off one another in such an intimate fashion, that an engineer engaged in the design of a bridge must be constantly aware of how each part of the design-rehabilitate-maintain process works in relationship to another. This text is intended to be more practical than theoretical. In terms of analytical techniques, there is no new ground broken in this book. Rather, the book is meant to synthesize and coalesce the broad range of material into a coherent document describing the entire bridge engineering process. The reader will notice this when perusing through the sections on such diverse, yet important, topics as project funding, inspection of bridges, preparation of contract documents, and the development of a Bridge Management System (BMS). The presentation of the material in this book is also somewhat different

PREFACE xxiii

Discussion of Presentation of Material Design Examples Presented as Calculation Sheets Sidebars Highlight Material in the Text

from the engineering texts we have become accustomed to. Although the graphical presentation of the subject matter may seem like a new approach, it is really a throwback to a style of text which was more prevalent 40 years ago. Design examples, for instance, are presented in a calculation sheet format, just as a designer would write them up in an actual bridge project. This technique has previously been used by authors like George Large in his excellent treatise on reinforced concrete design, which was first published in 1950 [Ref. 3.46]. Since the design examples have been separated from the text, they do not break the continuity of the discussion. This approach also has the benefit of not confusing the reader when perusing through the design sections, as can be the case when a calculation step is mistaken for an equation and vice versa. To the immediate right of each calculation sheet is an in-depth discussion of the steps taken on the particular sheet. Contained within each step outline are references to pertinent specifications and equations located within the text proper. The large physical dimensions of the text are specifically used to allow for the incorporation of sidebars to the left and right side of each facing page. The use of large margins, such as these, dates back even further than George Large's book. In what has euphemistically (and somewhat erroneously) become known as the dark ages, monks and scholars provided large margins around their text so that the author, or the people reading the document, could gloss the text. A "gloss" was a comment, explanation, or translation of the material located within the accompanying manuscript. In this vein, a variety of information is provided in each page's sidebars. Almost always there is a direct quote from the accompanying text which has been pulled out to act as a highlight of the information provided on the page and draw the reader's attention to an especially important fact or issue. Also included in the sidebars are design specifications which are relevant to the material being discussed on the page. This saves the reader from the task of constantly having to flip back and forth between pages. The structure of the design examples follows a similar logic. Within the sidebars, the reader will also find quotes from some of the reference material. These quotes are intended to act as an accent on the topics currently being discussed. It is hoped that the readers, like the reviewers of medieval manuscripts, will gloss the text with their own notes, commentary, and thoughts. No matter how important bridge engineering is, the subject matter can become a little dry sometimes. To break the monotony which will inevitably occur in any engineering text, Did You Know? sidebars are provided which offer relevant historical data, statistics, or other information about the subject matter currently being discussed, which the reader may or may not be aware of. To provide a real world slant on the information being covered, several separate discussion pieces have been included under the Design Perspective header. These discussions offer some current thinking on a variety of interesting and controversial issues such as the hazards of lead bridge paint and steel vs. concrete bridges. At the top of each page, three lines are provided which give a synopsis of the major topics discussed on a given page. This synopsis acts as a sort of onthe-fly outline. It is realized that engineering books are not so much read as they are referenced. Because of this, the information located in the margins of the document are intended to act as pointers, directing the reader's attention to the material contained within. Hopefully, as the reader flips back and forth, looking

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n what has euphemistically ... become known as the dark ages, monks and scholars provided large margins around their text so that the author, or the people reading the document, could gloss the text.

xxiv BRIDGE ENGINEERING

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he design, rehabilitation, and maintenance of highway bridges is, at least for this author, an exciting subject. More than that, however, the engineering of highway bridges is an important subject.

Engineering Books Are Referenced More Than Read Lexicon Acts as a Dictionar y of Bridge Terms Importance of Bridge Engineering

for the desired information, he or she will use the sidebars as tools in identifying pertinent information. Included at the end of the first section is a Bridge Engineering Lexicon. This lexicon acts as a glossary of pertinent bridge engineering terms. For the reader who is new to bridge design, it is important to spend time reviewing this list. Since most civil engineers possess a common background in structural design (at least from college experience), one of the first major hurdles that must be overcome is the development of a familiarity with the nomenclature used on a daily basis by bridge designers. For the most part, the definitions provided in the lexicon reappear throughout the course of the text. The lexicon should serve as a quick lookup table for readers so that they do not have to consult the index, flip to a page in the book, and then try to track down the definition they are looking for. The design, rehabilitation, and maintenance of highway bridges is, at least for this author, an exciting subject. More than that, however, the engineering of highway bridges is an important subject. From a distance, it is difficult to appreciate our dependence on highway bridges and the important role they, along with the highways they carry, play in our modern economy. The individuals charged with the responsibility of keeping these structures operational are faced with a daunting task. With limited resources and imposing constraints, somehow the job manages to get done. It is hoped that, in some small way, this text will help in the effort to design, rehabilitate, and maintain highway bridges, into the next century and beyond. Demetrios E. Tonias, P.E. Schenectady, New York March, 1994

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