Christian Menn

Prestressed Concrete Bridges

Translated and edited by Paul Gauvreau

Birkhauser Verlag Basel . Boston . Berlin

Originally published in 1986 under the title "Stahlbetonbriicken" by Springer­Verlag, Wien. © 1986 by Springer-Verlag, Wien.

Author's address: Christian Menn Professor of Civil Engineering Swiss Federal Institute of Technology Zurich (Switzerland)

Library of Congress Cataloging-in-Publication Data

Menn, Christian, 1927-[Stahlbetonbriicken. English) Prestressed concrete bridges / Christian Menn ; translation into English and edited by Paul Gauvreau. p. ern. Translation of: Stahlbetonbriicken. Includes bibliographical references (p. ) and index. ISBN-I3: 978-3-0348-9920-8 (U.S.). 1. Bridges, Concrete-Design and construction. 2. Reinforced concrete construction. I. Gauvreau, Paul. II. Title. TG340.M4613 1990 624' .257 -dc20

Deutsche Bibliothek Cataloging-in-Publication Data

Menn, Christian: Prestressed concrete bridges / Christian Menn. Transl. into Engl. and ed. by Paul Gauvreau. - Basel ; Boston ; Berlin : Birkhauser, 1990 Einheitssacht.: Stahlbetonbriicken (engl.) ISBN-13:978-3-0348-9920-8 e- ISBN-13:978-3-0348-9131-8 DOl: 10.10071978+0348-9131-8

This work is subject to copyright. All rights are reserved, whether the whole.or part of the material is concerned, specifically those of reprinting, re-use of illustrations, broadcasting, reproduction by photocopying machine or similar means, and storage in data banks. Under § 54 of the German Copyright Law where copies are made for other than private use a fee is payable to "Verwertungsgesellschaft Wort", Munich.

© 1990 Birkhiiuser Verlag AG Basel Softcover reprint of the hardcover 1st edition 1990

ISBN-13:978-3-0348-9920-8

Preface

This book was written to make the material presented in my book, Stahlbetonbrucken, accessible to a larger number of engineers throughout the world. A work in English, the logical choice for this task, had been contemplated as Stahlbetonbrucken was still in its earliest stages of preparation. The early success of Stahlbetonbrucken provided significant impetus for the writing of Prestressed Concrete Bridges, which began soon after the publication of its predecessor.

The present work is more than a mere translation of Stahlbetonbrucken. Errors in Stahlbetonbrucken that were detected after publication have been corrected. New material on the relation between cracking in concrete and corrosion of reinforce­ment, prestressing with unbonded tendons, skew-girder bridges, and cable-stayed bridges has been added. Most importantly, however, the presentation of the material has been extensively reworked to improve clarity and consistency. Prestressed Concrete Bridges can thus be regarded as a thoroughly new and improved edition of its predecessor.

This book is guided by the same philosophy as its German-language counterpart: quality in the design and construction of bridges is achieved through the application of a small number of fundamental principles. In the last decade, the issue of durability in bridges has grown in importance, giving new urgency to the need for quality. The deterioration of bridges is often due to deficiencies in design, building materials, detailing, or construction. An awareness of quality and how it is achieved is thus crucial to preventing a repetition of past mistakes in the rehabilitation of existing structures and the design of new ones. Analytical refinement for its own sake continues to be the primary obstacle to quality in design. The preference found throughout Stahlbetonbrucken for clear, simple, case-specific calculations over more general analyses of greater complexity has therefore been maintained in the present work.

Stahlbetonbrucken was largely based on direct experience gained from the design and construction of bridges in Switzerland over the past thirty years. As a result, much of the material discussed in the present work appears in a decidedly Swiss context. The main differences between this book and practise in other countries can be summarized as follows:

VI Preface

1. Loadings, assumptions of material behaviour, and rules for checking safety and serviceability have been taken directly from Swiss SIA Standards 160 and 162. No attempt has been made to adapt these aspects of the book to the standards or local practise of other countries, since, armed with an understanding of the fundamental principles of bridge design, the reader should have little difficulty in doing so for himself.

2. A unified theory of concrete design, which is now well established in Swiss practise, underlies this book. This theory provides one consistent set of rules for design, valid for structures in plain, reinforced, or prestressed concrete. One of the most important consequences of this approach is partial prestressing, by which the engineer is freed from arbitrary restrictions on tensile stresses in concrete at service load levels. Prestressing can thus be chosen to achieve certain specific objectives under service conditions, while contributing fully to re­sistance at ultimate limit state. These objectives are referred to in this book as prestressing concepts, a powerful tool which makes possible a rational use of prestressing. Engineers in countries where only full prestressing is allowed may find some of the material in this book somewhat frustrating, since many of the solutions presented are not workable without partial prestressing. It is hoped that a wider recognition of the value of partial prestressing will facilitate the adoption of the unified theory of concrete design throughout the world.

3. Loads, prestressing, and restrained or imposed deformations are treated identically in design in many parts of the world. Consistent with current design standards in Switzerland, this book makes a clear distinction between the three, which are denoted collectively as actions. An awareness of the differences among the three types of actions is essential to a proper understanding of structural behaviour.

Thanks are due to Guido Goseli for relettering the figures into English and drawing the new figures, and to Heinrich Schnetzer for assistance with coordi­nation during the final stages of production. The support and advice provided by the staff of Birkhauser Verlag is also greatly appreciated.

Finally, I would like to pay special tribute to my collaborator Paul Gauvreau, who transformed Stahlbetonbrucken into the present work. He brought to the task his skill as a translator, his good judgement as an editor, and his insight as a practising engineer. This rare combination of talents was instrumental in producing a book that is a significant improvement over its predecessor. His dedication, curiosity, and patience made possible the most cordial of professional collaborations, which was not only rewarding in itself, but is also reflected in the quality of this work.

Christian Menn Zurich 1989

Preface to the German Edition

"Everything should be made as simple as possible, but not simpler."

Albert Einstein

This book provides engineers with a comprehensive overview of the fundamental principles governing the design and construction of concrete bridges. Experience has shown that safety and quality are the direct result of the consistent and rational application of these principles. Refinement and volume of calculations, on the other hand, have no significant influence on quality or economy.

The book has its origins in lectures on the design of concrete bridges given to undergraduate and graduate students at the Department of Civil Engineering of the Swiss Federal Institute of Technology, Zurich. Its eight chapters cover the fundamentals of conceptual design, analysis, and detailed design of bridge superstructures and substructures.

Conceptual design is of primary importance to quality and economy_ The principles and objectives of conceptual design are therefore thoroughly discussed in the first chapters. In accordance with modern design standards, the concepts of safety and serviceability are clearly distinguished in discussions of analysis and detailed design. The proposed analytical models and methods of calculation are simple, clear, practical; and sufficiently accurate for design.

Truss models are used extensively throughout the book to establish the flow of forces in structural components. This method, known for decades yet "redis­covered" in recent years, was used consistently in my former design office and has proven itself in the analysis of many complex problems. Truss models are often more reliable than finite-element calculations, which are usually based on the assumption of isotropic, elastic material behaviour.

Reserves of structural resistance are considered in the verification of safety at ultimate limit state, in accordance with the theory of plasticity. It is recommended as a general rule, however, that designs be based on sectional forces obtained from the elastic solution. The greater the deviation of the design sectional forces from the elastic solution, the more important it becomes to ensure that the structure is capable of sufficient plastic deformations. Behaviour under service conditions and fatigue must also be given greater consideration as the difference between the design sectional forces and the elastic solution increases.

VIII Preface to the German Edition

Experience has shown that quality and durability of concrete structures cannot be achieved with careful analysis and design alone. The arrangement of reinforce­ment and detailing of individual structural components playa decisive role in this regard. For this reason, recommended details are presented and discussed throughout the book.

The most important diagrams for the calculation of slender compression members have been collected in the Appendix. The interaction diagrams can be used to calculate ultimate resistance of cross-sections and flexural stiffness at ultimate limit state. The latter is necessary for the calculation of second-order effects. A small number of important reference works has been listed, giving additional information and guidance for in-depth treatment of special problems.

Engineers today are faced with an explosion of technical information. Although this information will have beneficial effects on future developments, it has largely distracted engineers from the most fundamental principles. It is the purpose of this book to make engineers aware of these principles once again.

Acknowledgements

The extensive preparatory work for this book was supported financially by the Swiss Federal Institute of Technology, Zurich, the Swiss Federal Department of Transportation and Energy (Highway Research), Berne, and the Foundation for Scientific, Systematic Research in Concrete and Reinforced Concrete (Stiftungfor wissenschaftliche, systematische Forschung auf dem Gebiet des Beton- und Eisen­betonbaus), Zurich. Their support is gratefully acknowledged.

I would like to express my gratitude to members of the Institute of Structural Engineering at the Swiss Federal Institute of Technology and my personal collaborators, in particular Bruno Zimmerli for coordinating the work, Martin Kiiser, Thomas Keller, Christoph Kiinzli, Susanna Schenkel, Silvio Toscano, and Michael Wagner for their assistance in preparation of calculations, examples, and sketches, Guido Goseli for drafting the figures, and Sybille Burki and Rita Feusi for typing the manuscript. I am especially grateful to Springer-Verlag in Vienna for their excellent and understanding cooperation.

Christian Menn Zurich, November 1986

Contents

Preface v

Preface to the German Edition VII

1 Historical Overview . . . . . . . . . . . . . . . .

2 Economy and Aesthetics 49

2.1 Design Objectives 49

2.2 Economy 50 2.2.1 Life-Cycle Costs . 50 2.2.2 Construction Costs 52 2.2.3 Preliminary Estimates of Superstructure Costs 56

2.3 Aesthetics 58

Reference 64

3 Materials and Actions 65

3.1 Materials 65 3.1.1 Concrete 65 3.1.2 Reinforcing Steel . 77 3.1.3 Prestressing Steel . 80

3.2 Actions 83 3.2.1 Loads 83 3.2.2 Prestressing 89 3.2.3 Restrained Deformations 90

References 91

X Contents

4 Fundamentals of Analysis and Design 93

4.1 Design for Safety and Serviceability 93 4.1.1 Safety 93 4.1.2 Serviceability 95

4.2 Calculation of Sectional Forces 96 4.2.1 Fundamentals. 96 4.2.2 Sectional Forces Due to Loads, Prestressing, and Restrained

Deformations . 97

4.3 Calculation of the Resistance of the Cross-Section 103 4.3.1 Fundamentals . 103 4.3.2 Flexure and Axial Force 106 4.3.3 Shear. 108 4.3.4 Torsion . 111 4.3.5 Bending Resistance of Slabs and Tensile Resistance of Panels. 112

4.4 Safety of Beams, Slabs, and Panels 114 4.4.1 Beams 114 4.4.2 Slabs. 114 4.4.3 Panels 117

4.5 Detailing of Reinforcement 117 4.5.1 Anchorage and Splicing of Reinforcement 118 4.5.2 Detailing of Reinforcement at Joints of Rigid Frames 119 4.5.3 Flow of Forces in Panels 123 4.5.4 Flow of Forces in Box Girders and T-Girders 125

4.6 Prestressing 126 4.6.1 The Purpose of Prestressing 126 4.6.2 Methods of Prestressing 127 4.6.3 Post-Tensioning Systems 128 4.6.4 Detailing 131 4.6.5 Analysis of Prestressed Cross-Sections 135 4.6.6 Steel Stresses for Typical Loading States . 139 4.6.7 Prestressing with Unbonded Tendons 145 4.6.8 Loss of Prestress . 147 4.6.9 Prestressing Concepts 151

4.7 Long-Term Effects 152 4.7.1 Fundamentals . 152 4.7.2 Calculation of Deformations Due to Permanent Load 157 4.7.3 Redistribution of Sectional Forces Due to Change of

Structural System 157 4.7.4 Redistribution of Stress Due to Restrained Deformations

or Self-Equilibrating States of Stress 161

Contents

4.8 4.8.1 4.8.2 4.8.3 4.8.4 4.8.5 4.8.6

Serviceability Durability . Function Appearance Cracking Deformations Vibrations

References

5

5.1 5.1.1 5.1.2 5.1.3 5.1.4

5.2

5.3 5.3.1 5.3.2 5.3.3 5.3.4

Analysis and Design of Bridge Superstructures

Structural Models and Load Distribution General Ideas. . . . . . . . . . Torsion and Introduction of Loads in Single-Cell Box Girders Torsion and Eccentric Loads in Double-T Girders Structural Models for Bridge Superstructures . .

Structural Function of Cross-Section Components

Analysis and Design of Cross-Section Components Deck Slab . Webs ... Bottom Slab Diaphragms

References

6

6.1 6.1.1 6.1.2 6.1.3 6.1.4

6.2

Accessories .

Bearings. . General Remarks Structural Function of Bearings . Superstructure Displacements Bearing Layout .

Expansion Joints.

6.3 Drainage and Anchorage of Guardrails 6.3.1 Drainage . . . . . 6.3.2 Anchorage of Guardrails . . . .

6.4 Waterproofing and Wearing Surfaces

Reference

XI

167 167 171 172 174 192 195

210

211

211 211 216 231 238

242

245 245 256 264 266

275

277

277 277 279 280 284

285

288 288 289

289

292

XII Contents

7 Design and Construction of Special Bridge Types 293

7.1 Overview 293

7.2 Conventional Cast-in-Place Girder Bridges 295 7.2.1 Conceptual Design . . . 295 7.2.2 Design of the Cross-Section 296 7.2.3 Prestressing Concepts 301 7.2.4 Preliminary Design 301 7.2.5 Tendon Layouts . 302 7.2.6 Incrementally Launched Bridges 310

7.3 Girder Bridges with Precast Elements . 313 7.3.1 Conceptual Design . . . 313 7.3.2 Design of the Cross-Section 317 7.3.3 Prestressing Concepts 317 7.3.4 Preliminary Design 319

7.4 Cantilever-Constructed Girder Bridges 323 7.4.1 Conceptual Design . . . 323 7.4.2 Design of the Cross-Section 325 7.4.3 Prestressing Concept 330 7.4.4 Tendon Layout 332 7.4.5 Preliminary Design and Special Design Considerations 334 7.4.6 Calculation of Camber and Casting Elevations. 337

7.5 Skew Girder Bridges 341 7.5.1 Conceptual Design 341 7.5.2 Calculation of the Sectional Forces 347 7.5.3 Prestressing Concepts and Tendon Layouts. 361

7.6 Curved Girder Bridges . 365 7.6.1 Conceptual Design 365 7.6.2 Analysis. 368 7.6.3 Transformation of Torque into Torsional Sectional Forces 372 7.6.4 Prestressing. 376 7.6.5 Prestressing Concept and Tendon Layout 379

7.7 Arch Bridges 382 7.7.1 Conceptual Design 382 7.7.2 Design of the Cross-Section 385 7.7.3 Prestressing Concept and Tendon Layout 386 7.7.4 Preliminary Design 387

7.8 Frame Bridges 394 7.8.1 Conceptual Design 394 7.8.2 Prestressing Concepts and Tendon Layouts. 399

Contents

7.9 7.9.1 7.9.2 7.9.3 7.9.4 7.9.5

7.10 7.10.1 7.10.2 7.10.3 7.10.4 7.10.5 7.10.6

Slab Bridges . . . . . Conceptual Design . . . Design of the Cross-Section Prestressing Concept Design . . . . . Reinforcement Layout

Cable-Stayed Bridges Conceptual Design . Cables and Anchorages Analysis and Design. Stability. . . . . Dynamic Behaviour . Construction

References

8

8.1 8.1.1 8.1.2 8.1.3 8.1.4 8.1.5 8.1.6 8.1.7 8.1.8 8.1.9

8.2 8.2.1 8.2.2 8.2.3 8.2.4 8.2.5

Analysis and Design of Bridge Substructures .

Piers. . . . . . . . . . . . . . General Ideas. . . . . . . . . . . Second-Order Analysis of Slender Reinforced Concrete Columns Calculation of Ultimate Resistance for Flexure and Axial Force Flexural Stiffness of Reinforced Concrete Sections Imposed Deformations. . . Design at Ultimate Limit State Use of Design Aids Special Cases . Flexible Systems

Foundations . General Remarks. Spread Footings . Shaft Foundations Cofferdams. . . Pile Foundations.

References

Appendix: Diagrams for the Design of Slender Columns

A1 Use of Diagrams. A2 Notation

XIII

401 401 404 405 405 410

413 413 421 426 428 432 435

438

439

439 439 440 456 462 469 472 474 479 482

494 494 494 496 502 504

506

507

507 509

XIV

A3 A4 A5

Buckling Diagrams . . . . . . . . . . . . . mR - nR Interaction Diagrams . . . . . . . . . k", Diagrams for the Reduction of Stiffness Due to Creep

Contents

510 512 524

Index . . . . . . . . . . . . . . . . . . . . . . . 525