Bridge engineering handbook edited by wai fah chen, lian duan

Section IV, Seismic Design, providesearthquake geotechnical and damage considerations, seismic analysis and design, seismic isolation andenergy dissipation, soil–structure–foundation int

Bridge Engineering Handbook

Bridge Engineering Handbook

Edited byWai-Fah ChenLian DuanCRC PressBoca Raton London New York Washington, D C

Acquiring Editor: Nora Konopka Project Editors: Carol Whitehead, Sylvia Wood Marketing Managers: Barbara Glunn, Jane Lewis, Arline Massey, Jane Stark Cover design: Jonathan Pennell

Manufacturing: Carol Slatter

Library of Congress Cataloging-in-Publication Data

Chen, Wai-Fah, Duan, Lian Bridge engineering handbook / edited by Wai-Fah Chen, Lian Duan.

p cm.

Includes bibliographical references and index.

ISBN 0-8493-7434-0 (alk paper)

1 Bridges—Design and construction I Chen, Wai-Fah, 1936 - II

Duan, Lian.

TG145 - B85 1999

CIP This book contains information obtained from authentic and highly regarded sources Reprinted material is quoted with permission, and sources are indicated A wide variety of references are listed Reasonable efforts have been made to publish reliable data and information, but the author and the publisher cannot assume responsibility for the validity of all materials

or for the consequences of their use.

Neither this book nor any part may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, microfilming, and recording, or by any information storage or retrieval system, without prior permission in writing from the publisher.

All rights reserved Authorization to photocopy items for internal or personal use, or the personal or internal use of specific clients, may be granted by CRC Press LLC, provided that $.50 per page photocopied is paid directly to Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923 USA The fee code for users of the Transactional Reporting Service is ISBN 0-8493-7434-0/00/$0.00+$.50 The fee is subject to change without notice For organizations that have been granted a photocopy license by the CCC, a separate system of payment has been arranged.

The consent of CRC Press LLC does not extend to copying for general distribution, for promotion, for creating new works, or for resale Specific permission must be obtained in writing from CRC Press LLC for such copying.

Direct all inquiries to CRC Press LLC, 2000 Corporate Blvd., N.W., Boca Raton, Florida 33431.

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© 2000 by CRC Press LLC

No claim to original U.S Government works International Standard Book Number 0-8493-7434-0 Library of Congress Card Number 99-3175 Printed in the United States of America 1 2 3 4 5 6 7 8 9 0 Printed on acid-free paper

Among all engineering subjects, bridge engineering is probably the most difficult on which to compose

a handbook because it encompasses various fields of arts and sciences It not only requires knowledgeand experience in bridge design and construction, but often involves social, economic, and politicalactivities Hence, I wish to congratulate the editors and authors for having conceived this thick volumeand devoted the time and energy to complete it in such short order Not only is it the first handbook ofbridge engineering as far as I know, but it contains a wealth of information not previously available tobridge engineers It embraces almost all facets of bridge engineering except the rudimentary analyses andactual field construction of bridge structures, members, and foundations Of course, bridge engineering

is such an immense subject that engineers will always have to go beyond a handbook for additionalinformation and guidance

I may be somewhat biased in commenting on the background of the two editors, who both came fromChina, a country rich in the pioneering and design of ancient bridges and just beginning to catch upwith the modern world in the science and technology of bridge engineering It is particularly to theeditors’ credit to have convinced and gathered so many internationally recognized bridge engineers tocontribute chapters At the same time, younger engineers have introduced new design and constructiontechniques into the treatise

This Handbook is divided into seven sections, namely:

May I advise each bridge engineer to have a desk copy of this volume with which to survey and examineboth the breadth and depth of bridge engineering

T Y Lin

Professor Emeritus, University of California at Berkeley

Chairman, Lin Tung-Yen China, Inc

The areas of bridge engineering include planning, analysis and design, construction, maintenance, andrehabilitation To provide engineers a well-organized, user-friendly, and easy-to-follow resource, theHandbook is divided into seven sections Section I, Fundamentals, presents conceptual design, aesthetics,planning, design philosophies, bridge loads, structural analysis, and modeling Section II, Superstructure Design, reviews how to design various bridges made of concrete, steel, steel-concrete composites, andtimbers; horizontally curved, truss, arch, cable-stayed, suspension, floating, movable, and railroadbridges; and expansion joints, deck systems, and approach slabs Section III, Substructure Design, addressesthe various substructure components: bearings, piers and columns, towers, abutments and retainingstructures, geotechnical considerations, footings, and foundations Section IV, Seismic Design, providesearthquake geotechnical and damage considerations, seismic analysis and design, seismic isolation andenergy dissipation, soil–structure–foundation interactions, and seismic retrofit technology and practice.

Section V, Construction and Maintenance, includes construction of steel and concrete bridges, tures of major overwater bridges, construction inspections, maintenance inspection and rating, strength-ening, and rehabilitation Section VI, Special Topics, addresses in-depth treatments of some importanttopics and their recent developments in bridge engineering Section VII, Worldwide Practice, provides theglobal picture of bridge engineering history and practice from China, Europe, Japan, and Russia to the U.S.The Handbookstresses professional applications and practical solutions Emphasis has been placed

substruc-on ready-to-use materials, and special attentisubstruc-on is given to rehabilitatisubstruc-on, retrofit, and maintenance TheHandbook contains many formulas and tables that give immediate answers to questions arising frompractical works It describes the basic concepts and assumptions, omitting the derivations of formulasand theories, and covers both traditional and new, innovative practices An overview of the structure,organization, and contents of the book can be seen by examining the table of contents presented at thebeginning, while an in-depth view of a particular subject can be seen by examining the individual table

of contents preceding each chapter References at the end of each chapter can be consulted for detailed studies

more-The chapters have been written by many internationally known authors from different countriescovering bridge engineering practices, research, and development in North America, Europe, and thePacific Rim This Handbook may provide a glimpse of a rapidly growing trend in global economy inrecent years toward international outsourcing of practice and competition in all dimensions of engineer-ing In general, the Handbook is aimed toward the needs of practicing engineers, but materials may bereorganized to accommodate undergraduate and graduate level bridge courses The book may also beused as a survey of the practice of bridge engineering around the world

The authors acknowledge with thanks the comments, suggestions, and recommendations during thedevelopment of the Handbook by Fritz Leonhardt, Professor Emeritus, Stuttgart University, Germany;Shouji Toma, Professor, Horrai-Gakuen University, Japan; Gerard F Fox, Consulting Engineer; Jackson

L Durkee, Consulting Engineer; Michael J Abrahams, Senior Vice President, Parsons, Brinckerhoff,Quade & Douglas, Inc.; Ben C Gerwick, Jr., Professor Emeritus, University of California at Berkeley;Gregory F Fenves, Professor, University of California at Berkeley; John M Kulicki, President and ChiefEngineer, Modjeski and Masters; James Chai, Senior Materials and Research Engineer, California Depart-ment of Transportation; Jinrong Klang, Senior Bridge Engineer, URS Greiner; and David W Liu, Prin-cipal, Imbsen & Associates, Inc

We wish to thank all the authors for their contributions and also to acknowledge at CRC Press NoraKonopka, Acquiring Editor, and Carol Whitehead and Sylvia Wood, Project Editors

Wai-Fah Chen Lian Duan

Wai-Fah Chen is a George E Goodwin Distinguished Professor ofCivil Engineering and Head of the Department of Structural Engi-neering, School of Civil Engineering at Purdue University He receivedhis B.S in civil engineering from the National Cheng-Kung University,Taiwan, in 1959, M.S in structural engineering from Lehigh Univer-sity, Bethlehem, Pennsylvania in 1963, and Ph.D in solid mechanicsfrom Brown University, Providence, Rhode Island in 1966

Dr Chen’s research interests cover several areas, including constitutivemodeling of engineering materials, soil and concrete plasticity, struc-tural connections, and structural stability He is the recipient ofnumerous engineering awards, including the AISC T.R Higgins Lec-tureship Award, the ASCE Raymond C Reese Research Prize, and theASCE Shortridge Hardesty Award He was elected to the NationalAcademy of Engineering in 1995, and was awarded an HonoraryMembership in the American Society of Civil Engineers in 1997 He was most recently elected to theAcademia Sinica in Taiwan

Dr Chen is a member of the Executive Committee of the Structural Stability Research Council, theSpecification Committee of the American Institute of Steel Construction, and the editorial board of sixtechnical journals He has worked as a consultant for Exxon’s Production and Research Division onoffshore structures, for Skidmore, Owings and Merril on tall steel buildings, and for World Bank on theChinese University Development Projects

A widely respected author, Dr Chen’s works include Limit Analysis and Soil Plasticity (Elsevier, 1975),the two-volume Theory of Beam-Columns (McGraw-Hill, 1976–77), Plasticity in Reinforced Concrete

(McGraw-Hill, 1982), Plasticity for Structural Engineers (Springer-Verlag, 1988), and Stability Design of Steel Frames (CRC Press, 1991) He is the editor of two book series, one in structural engineering andthe other in civil engineering He has authored or coauthored more than 500 papers in journals andconference proceedings He is the author or coauthor of 18 books, has edited 12 books, and has contrib-uted chapters to 28 other books His more recent books are Plastic Design and Second-Order Analysis of Steel Frames (Springer-Verlag, 1994), the two-volume Constitutive Equations for Engineering Materials

(Elsevier, 1994), Stability Design of Semi-Rigid Frames (Wiley-Interscience, 1995), and LRFD Steel Design Using Advanced Analysis (CRC Press, 1997) He is editor-in-chief of The Civil Engineering Handbook (CRCPress, 1995, winner of the Choice Outstanding Academic Book Award for 1996, Choice Magazine), andthe Handbook of Structural Engineering (CRC Press, 1997)

Lian Duan is a Senior Bridge Engineer with the California ment of Transportation, U.S., and Professor of Structural Engineer-ing at Taiyuan University of Technology, China

Depart-He received his B.S in civil engineering in 1975, M.S in structuralengineering in 1981 from Taiyuan University of Technology, andPh.D in structural engineering from Purdue University, West Lafay-ette, Indiana in 1990 Dr Duan worked at the Northeastern ChinaPower Design Institute from 1975 to 1978

Dr Duan’s research interests cover areas including inelastic behavior

of reinforced concrete and steel structures, structural stability andseismic bridge analysis and design He has authored or coauthoredmore than 60 papers, chapters, and reports, and his research hasfocused on the development of unified interaction equations for steelbeam-columns, flexural stiffness of reinforced concrete members, effective length factors of compressionmembers, and design of bridge structures

Dr Duan is also an esteemed practicing engineer He has designed numerous building and bridgestructures Most recently, he has been involved in the seismic retrofit design of the San Francisco-OaklandBay Bridge West spans and made significant contributions to the project He is coeditor of the Structural Engineering Handbook CRCnetBase 2000 (CRC Press, 2000)

Department of Civil Engineering

and Operations Research

Chun S Cai

Florida Department of Transportation Tallahassee, Florida

James Chai

California Department of Transportation Sacramento, California

Nan Deng

Bechtel Corporation San Francisco, California

Robert J Dexter

Department of Civil Engineering University of Minnesota Minneapolis, Minnesota

Sacramento, California

Mahmoud Fustok

California Department of Transportation Sacramento, California

Ben C Gerwick, Jr.

Ben C Gerwick, Inc.

Consulting Engineers San Francisco, California

Department of Civil Engineering

South China University of

Department of Civil Engineering

California State University

Long Beach, California

Fritz Leonhardt

California Department of Transportation Sacramento, California

Fang Li

California Department of Transportation Sacramento, California

Department of Civil Engineering

Case Western Reserve University

Cleveland, Ohio

Joseph M Plecnik

Department of Civil Engineering

California State University

Long Beach, California

Oleg A Popov

Joint Stock Company Giprotransmost (Tramos) Moscow, Russia

Zolan Prucz

Modjeski and Masters, Inc.

New Orleans, Louisiana

Mark L Reno

California Department of Transportation Sacramento, California

James Roberts

California Department of Transportation Sacramento, California

Norman F Root

California Department of Transportation Sacramento, California

Yusuf Saleh

California Department of Transportation Sacramento, California

Thomas E Sardo

California Department of Transportation Sacramento, California

Gerard Sauvageot

J Muller International San Diego, California

Charles Scawthorn

EQE International Oakland, California

Charles Seim

T Y Lin International San Francisco, California

Vadim A Seliverstov

Joint Stock Company Giprotransmost (Tramos) Moscow, Russia

Li-Hong Sheng

California Department of Transportation Sacramento, California

Donald F Sorgenfrei

Modjeski and Masters, Inc.

New Orleans, Louisiana

Jim Springer

California Department of Transportation Sacramento, California

Shawn Sun

California Department of Transportation Sacramento, California

Shouji Toma

Department of Civil Engineering Hokkai-Gakuen University Sapporo, Japan

M S Troitsky

Department of Civil Engineering Concordia University

Montreal, Quebec Canada

Keh-Chyuan Tsai

Department of Civil Engineering National Taiwan University Taipei, Taiwan

Republic of China

Public Works Research Institute

Tsukuba Science City, Japan

Tetsuya Yabuki

Department of Civil Engineering and Architecture

University of Ryukyu Okinawa, Japan

Quansheng Yan

College of Traffic and Communication South China University of Technology

Ke Zhou

California Department of Transportation Sacramento, California

1.4 Remarks and Conclusions

2 Bridge Aesthetics — Basics Fritz Leonhardt

2.1 Introduction

2.2 The Terms

2.3 Do Objects Have Aesthetic Qualities?

2.4 How Do Humans Perceive Aesthetic Values?

2.5 The Cultural Role of Proportions

2.6 How Do We Perceive Geometric Proportions?

2.7 Perception of Beauty in the Subconscious

2.8 Aesthetic Judgment and Taste

2.9 Characteristics of Aesthetic Qualities Lead to Guidelines for Designing

2.10 Aesthetics and Ethics

2.11 Summary

3 Bridge Aesthetics — Structural Art David P Billington and

Frederick Gottemoeller

3.1 Introduction

3.2 The Engineer’s Aesthetic and Structural Art

3.3 The Three Dimensions of Structure

3.4 Structure and Architecture

3.5 Application to Everyday Design

3.6 The Role of Case Studies in Bridge Design

3.7 Case Study in Colorado: Buckley Road over I-76

3.8 Achieving Structural Art in Modern Society: Computer Analysis and

Design Competition

3.9 The Engineer’s Goal

4 Planning of Major Fixed Links Klaus H Ostenfeld, Dietrich L Hommel,

Dan Olsen, and Lars Hauge

4.1 Introduction

4.2 Project Development

4.3 Project Basis

4.4 Recent Examples of Fixed Links

5 Design Philosophies for Highway Bridges John M Kulicki

6.6 Effects Due to Superimposed Deformations

6.7 Exceptions to Code-Specified Design Loads

7 Structural Theory Xila Liu and Leiming Zhang

7.6 Substructuring and Symmetry Consideration

8 Structural Modeling Alexander Krimotat and Li-Hong Sheng

8.1 Introduction

8.2 Theoretical Background

8.3 Modeling

8.4 Summary

SECTION II Superstructure Design

9 Reinforced Concrete Bridges Jyouru Lyang, Don Lee, and John Kung

10 Prestressed Concrete Bridges Lian Duan, Kang Chen, and Andrew Tan

11.2 Balanced Cantilever Girder Bridges

11.3 Progressive and Span-by-Span Constructed Bridges

11.4 Incrementally Launched Bridges

11.5 Arches, Rigid Frames, and Truss Bridges

11.6 Segmental Cable-Stayed Bridges

11.7 Design Considerations

11.8 Seismic Considerations

11.9 Casting and Erection

11.10 Future of Segmental Bridges

12 Steel–Concrete Composite I-Girder Bridges Lian Duan, Yusuf Saleh, and

12.6 Other Design Considerations

13 Steel–Concrete Composite Box-Girder Bridges Yusuf Saleh and Lian Duan

15 Horizontally Curved Bridges Ahmad M Itani and Mark L Reno

15.1 Introduction

15.2 Structural Analysis for Curved Bridges

15.3 Curved Steel I-Girder Bridges

15.4 Curved Steel Box-Girder Bridges

15.5 Curved Concrete Box-Girder Bridges

16 Highway Truss Bridges John M Kulicki

17.2 Short History of Arch Bridges

17.3 Types of Arch Bridges

17.4 Examples of Typical Arch Bridges

17.5 Analysis of Arch Bridges

17.6 Design Considerations for an Arch Bridge

18.5 Field Measurement and Coatings

19 Cable-Stayed Bridges Man-Chung Tang

20.3 Types of Timber Bridges

20.4 Basic Design Concepts

21 Movable Bridges Michael J Abrahams

22.5 Structural Design and Analysis

22.6 Fabrication and Construction

23.2 Railroad Bridge Philosophy

23.3 Railroad Bridge Types

25.4 Small Movement Range Joints

25.5 Medium Movement Range Joints

25.6 Large Movement Range Joints

25.7 Construction and Maintenance

SECTION III Substructure Design

26 Bearings Johnny Feng and Hong Chen

26.1 Introduction

26.2 Types of Bearings

26.3 Selection of Bearings

26.4 Design of Elastomeric Bearings

27 Piers and Columns Jinrong Wang

30.2 Field Exploration Techniques

30.3 Defining Site Investigation Requirements

30.4 Development of Laboratory Testing Program

30.5 Data Presentation and Site Characterization

31 Shallow Foundations James Chai

31.1 Introduction

31.2 Design Requirements

31.3 Failure Modes of Shallow Foundations

31.4 Bearing Capacity for Shallow Foundations

31.5 Stress Distribution Due to Footing Pressures

31.6 Settlement of Shallow Foundations

31.7 Shallow Foundations on Rock

31.8 Structural Design of Spread Footings

32 Deep Foundations Youzhi Ma and Nan Deng

32.1 Introduction

32.2 Classification and Selection

32.3 Design Considerations

32.4 Axial Capacity and Settlement — Individual Foundation

32.5 Lateral Capacity and Deflection — Individual Foundation

32.6 Grouped Foundations

32.7 Seismic Design

SECTION IV Seismic Design

33 Geotechnical Earthquake Considerations Steven Kramer and Charles

Scawthorn

33.1 Introduction

33.2 Seismology

33.3 Measurement of Earthquakes 33-3

33.4 Strong Motion Attenuation and Duration

33.5 Probabilistic Seismic Hazard Analysis

34.2 Effects of Site Conditions

34.3 Correlation of Damage with Construction Era

34.4 Effects of Changes in Condition

34.5 Effects of Structural Configuration

34.6 Unseating at Expansion Joints

34.7 Damage to Superstructures

34.8 Damage to Bearings

34.9 Damage to Substructures

34.10 Summary

35 Dynamic Analysis Rambabu Bavirisetty, Murugesu Vinayagamoorthy,

and Lian Duan

35.1 Introduction

35.2 Single-Degree-of-Freedom System

35.3 Multidegree-of-Freedom System

35.4 Response Spectrum Analysis

35.5 Inelastic Dynamic Analysis

35.6 Summary

36 Nonlinear Analysis of Bridge Structures Mohamed Akkari and Lian Duan

36.1 Introduction

36.2 Analysis Classification and General Guidelines

36.3 Geometrical Nonlinearity Formulations

36.4 Material Nonlinearity Formulations

36.5 Nonlinear Section Analysis

36.6 Nonlinear Frame Analysis

36.7 Practical Applications

37 Seismic Design Philosophies and Performance-Based Design Criteria

Lian Duan and Fang Li

37.1 Introduction

37.2 Design Philosophies

37.3 No-Collapse-Based Design Approaches

37.4 Performance-Based Design Approaches

37.5 Sample Performance-Based Criteria

37.6 Summary

38 Seismic Design of Reinforced Concrete Bridges Yan Xiao

38.1 Introduction 38-1

38.2 Typical Column Performance

38.3 Flexural Design of Columns

38.4 Shear Design of Columns

38.5 Moment-Resisting Connection between Column and Beam

38.6 Column Footing Design

39 Seismic Design of Steel Bridges Chia-Ming Uang, Keh-Chyuan Tsai, and

Michel Bruneau

39.1 Introduction

39.2 Ductile Moment-Resisting Frame (MRF) Design

39.3 Ductile Braced Frame Design

39.4 Stiffened Steel Box Pier Design

41 Seismic Isolation and Supplemental Energy Dissipation Rihui Zhang

41.1 Introduction

41.2 Basic Concepts, Modeling, and Analysis

41.3 Seismic Isolation and Energy Dissipation Devices

41.4 Performance and Testing Requirements

41.5 Design Guidelines and Design Examples

41.6 Recent Developments and Applications

42.4 Seismic Inputs to SFSI System

42.5 Characterization of Soil–Foundation System

42.6 Demand Analysis Procedures

42.7 Demand Analysis Examples

44.2 History of Earthquake Damage and Development of Seismic Design Methods

44.3 Damage of Highway Bridges Caused by the Hyogo-ken Nanbu Earthquake

44.4 1996 Seismic Design Specifications of Highway Bridges

44.5 Seismic Retrofit Practices for Highway Bridges

SECTION V Construction and Maintenance

45 Steel Bridge Construction Jackson Durkee

45.1 Introduction

45.2 Construction Engineering in Relation to Design Engineering

45.3 Construction Engineering Can Be Critical

45.4 Premises and Objectives of Construction Engineering

45.5 Fabrication and Erection Information Shown on Design Plans

45.6 Erection Feasibility

45.7 Illustrations of Challenges in Construction Engineering

45.8 Obstacles to Effective Construction Engineering

45.9 Examples of Inadequate Construction Engineering Allowances and Effort

45.10 Considerations Governing Construction Engineering Practices

45.11 Camber considerations

45.12 Two General Approaches to Fabrication and Erection of Bridge Steelwork

45.13 Example of Arch Bridge Construction

45.14 Which Construction Procedure is to be Preferred?

45.15 Example of Suspension Bridge Cable Construction

45.16 Example of Cable-Stayed Bridge Construction

45.17 Field Checking at Critical Erection Stages

45.18 Determination of Erection Strength Adequacy

45.19 Philosophy of the Erection Rating Factor

45.20 Minimum Erection Rating Factors

45.21 Deficiencies of Typical Construction Procedure Drawings and Instructions

45.22 Shop and Field Liaison by Construction Engineers

45.23 Comprehensive Bridge Erection-Engineering Specifications

45.24 Standard Conditions for Contracting

46.2 Effective Construction Engineering

46.3 Construction Project Management

46.4 Major Construction Considerations

47.2 Large Diameter Tubular Piles

47.3 Cofferdams for Bridge Piers

48 Bridge Construction Inspection Mahmoud Fustok and Masoud Alemi

49.5 Fundamentals of Bridge Rating

49.6 Superstructure Rating Examples

50.4 Improving the Strength of Various Bridge Members

50.5 Post-Tensioning Various Bridge Components

50.6 Developing Additional Bridge Continuity

50.7 Recent Developments

50.8 Summary

SECTION VI Special Topics

51 Applications of Composites in Highway Bridges Joseph M Plecnik and

Oscar Henriquez

51.1 Introduction

51.2 Material Properties

51.3 Advantages and Disadvantages of Composites in Bridge Applications

51.4 Pultruded Composite Shapes and Composite Cables

51.5 FRP Reinforcing Bars for Concrete

51.6 Composite Bridge Decks

51.7 Wearing Surface for a Composite Deck

51.8 Composite Bridge Structural Systems

51.9 Column Wrapping Using Composites

51.10 Strengthening of Bridge Girders Using CFRP Laminates

51.11 Composite Highway Light Poles

51.12 Nondestructive Evaluation of Composite Bridge Systems

51.13 Summary

52 Effective Length of Compression Members Lian Duan and Wai-Fah Chen

52.1 Introduction

52.2 Isolated Columns

52.3 Framed Columns — Alignment Chart Method

52.4 Modifications to Alignment Charts

52.5 Framed Columns — Alternative Methods

52.6 Crossing Frame System

52.7 Latticed and Built-Up Members

54.3 Data Base of Steel Weights

54.4 Statistics of Steel Weights

55.2 Weigh-in-Motion Truck Weight Measurement

55.3 Fatigue Load Measurement

55.4 Dynamic Load Measurement

55.5 Summary

56 Impact Effect of Moving Vehicles Mingzhu Duan, Philip C Perdikaris, and

Wai-Fah Chen

56.1 Introduction

56.2 Consideration of Impact Effect in Highway Bridge Design

56.3 Consideration of Impact Effect in Railway Bridge Design

56.4 Free Vibration Analysis

56.5 Forced Vibration Analysis under Moving Load

57 Wind Effects on Long-Span Bridges Chun S Cai and Serge Montens

58.2 Determination of Designed Cable Forces

58.3 Adjustment of the Cable Forces

58.4 Simulation of Construction Process

58.5 Construction Control

58.6 An Engineering Example

59 Active Control in Bridge Engineering Zaiguang Wu

59.1 Introduction

59.2 Typical Control Configurations and Systems

59.3 General Control Strategies and Typical Control Algorithms

59.4 Case Studies

59.5 Remarks and Conclusions

60 Vessel Collision Design of Bridges Michael Knott and Zolan Pruca

60.1 Introduction

60.2 Initial Planning

60.3 Waterway Characteristics

60.4 Vessel Traffic Characteristics

60.5 Collision Risk Analysis

60.6 Vessel Impact Loads

60.7 Bridge Analysis and Design

60.8 Bridge Protection Measures

60.9 Conclusions

61 Bridge Hydraulics Jim Springer and Ke Zhou

SECTION VII Worldwide Practice

63 Bridge Design Practice in China Guohao Li and Rucheng Xiao

64.6 Future European Bridges

65 Design Practice in Japan Masatsugu Nagai, Tetsuya Yabuki, and

65.7 Long-Span Bridges (Honshu–Shikoku Bridge Project)

65.8 New Bridge Technology Relating to Special Bridge Projects

65.9 Summary

66 Design Practice in Russia Simon A Blank , Oleg A Popov, and

Vadim A Seliverstov

66.1 Introduction

66.2 Historical Evolution

66.3 Modern Development

66.4 Design Theory and Methods

66.5 Inspection and Test Techniques

66.6 Steel and Composite Bridges

67.2 Early U.S Bridges

67.3 The Canal Era

67.4 The Railroad Era

67.5 The Motor Car Era

67.6 The Interstate Era

67.7 Era of the Signature Bridge

67.8 Epilogue

Section I

Fundamentals

Conceptual Bridge Design

1.1 Introduction 1.2 Preliminary Design Introduction • General Considerations for the Design

of Bridge Schemes • Theoretical Basic Method of Preliminary Design • Choice of Final Alternative for Reinforced–Concrete Bridges

1.3 Final DesignBasic Trends in the Design of Bridges • Creative Trends • Practical Trends • Basic Assumptions of Design • Basic Requirement of the Bridge under Design • Aesthetic Requirements • Requirement for Scientific Research • Basic Parameters of the Bridge • Bridge System • Size of Separate System • Type of Span Construction • Type of Supports

1.4 Remarks and Conclusions

1.1 Introduction

Planning and designing of bridges is part art and part compromise, the most significant aspect ofstructural engineering It is the manifestation of the creative capability of designers and demonstratestheir imagination, innovation, and exploration [1,2] The first question designers have to answer iswhat kind of structural marvel bridge design are they going to create?

The importance of conceptual analysis in bridge-designing problems cannot be emphasizedstrongly enough The designer must first visualize and imagine the bridge in order to determine itsfundamental function and performance

Without question, the factors of safety and economy shape the bridge designer’s thought in avery significant way The values of technical and economic analysis are indisputable, but they donot cover the whole design process

Bridge design is a complex engineering problem The design process includes consideration ofother important factors, such as choice of bridge system, materials, dimensions, foundations, aes-thetics, and local landscape and environment To investigate these issues and arrive at the bestsolution, the method of preliminary design is the subject of the discussion in this chapter

M S Troitsky

Concordia University

1.2 Preliminary Design

1.2.1 Introduction

What is preliminary design? Basically, the design process of bridges consists of two major parts: (1)the preliminary design phase and (2) the final design phase The first design phase is discussed inthis section and the final design phase is discussed in Section 1.3 in more detail

The preliminary design stage (see Tables 1.1 and 1.2)consists of a comprehensive search of currentpractical and analytical applications of old and new methods in structural bridge engineering Thefinal design stage consists of a complete treatment of a new project in all its aspects This includesany material, steel, or concrete problems The important argument is that with this approach asignificant savings in design effort can be easily achieved, particularly in the final stage

In order to plan and design a bridge, it is necessary first to visualize it The fundamental creativitylies in the imagination This is largely reflected by the designer’s creativity and the designer’s pastexperience and knowledge Also, the designer’s concept may be based on knowledge gained fromcomparisons of different bridge schemes

Generally, the designer approaches the problem successively, in two steps In preliminary design,the first and the most important part is the creation of bridge schemes The second step is to checkschemes and sketch them in a drawing It will then be possible to determine other design needs

An examination process is then carried out for other design requirements (e.g., local conditions,span systems, construction height, profile, etc.) From an economics point of view, choice of spanstructure, configuration, etc is very essential From the cost and aesthetics prospective, the viewagainst the local environment is important Completing these two steps yields the desired bridgescheme that satisfies the project proposal [3]

In the preliminary design stage it is also required to find a rational scientific analysis scheme forthe conceived design Thus, an essential part of preliminary design is to select and refine variousschemes in order to select the most appropriate one This is not an easy task since there are noexisting formulas and solution It is based mainly on the designer’s experience and the requirementsdictated by the project

The final stage requires a detailed study and analysis of structural behavior and stability Economyand safety are also important aspects in bridge design, but considerable attention must be given todetailed study for the analysis, which involves the final choices of the structural system, dimensions,material, system of spans, location of foundations, wind factor, and many others

However, the difference in preliminary schemes if all analysis is done accurately should not besubstantial Therefore, it is very important to have, from the first step, the design calculation exactand complete The designer workload can be dramatically reduced through use of auxiliary coeffi-cients These coefficients can be used if the chosen scheme needs to be modified

Design calculation is done on the basis of structural mechanics Usually the analysis starts withthe deck, stringers, and transverse beams which determine the weight of the deck Final analysisincludes a check of the main load-carrying members, determination of various loads and theireffects, total weight, and analysis of bearings Parallel to the analysis, correction of the initialconstruction scheme is normally carried out

However, at the preliminary design stage it is only necessary to explain the characteristics of thealternatives The comparison is normally based upon the weight and cost of the structure It shouldalso be highlighted that at this stage the weight of the structure cannot be determined with absoluteprecision It is normally estimated on the basis of experimental coefficients

As mentioned earlier, the aim of preliminary design is to compare various design schemes Thiscan be achieved efficiently by using computers The designer can create a number of rational schemesand alternatives in a short period of time A critical comparison between the various schemes shouldthen be made However, this is not an easy process and it is necessary to go to the next step Variouscomponents of each scheme, such as the deck, the spans, supports, etc should be compared witheach other It is important at this stage that the designer be able to visualize each component in the

scheme, sketch it, and check its rationality, applicability, and economy Following this, the analysisand drawings can be adjusted and corrected.

Finally, the chosen scheme should undergo a detailed design in order to establish the structure

of the bridge The analysis is applied to each component of the bridge and to the whole structure.Each part should be visualized first by the designer, sketched, analyzed, and checked for feasibility.Then it should be modified if necessary In each case, the most beneficial alternative should bechosen It is a very sensitive task because it is not easy to find immediate answers and the requiredsolutions The problem of making final choices could only be solved on the basis of generalconsiderations and designer’s particular point of view, which is undoubtedly based on personalexperience and knowledge as well as professional intuition

The sequence of analysis in detailed final design remains the same as for preliminary design exceptthat it is more complete The bridge structure at this stage has a physical meaning since each parthas been formed and detailed on paper Finally, the weight is estimated considering the actualvolume of the bridge elements and is documented in a special form referred to as “specifications”

or a list of weights The specifications generally should be drafted at the end of the project Thissequence leads to the final stage of the project, but the process is still incomplete The project willreach its final form only at the construction stage For this reason, it is worth mentioning that thedesigner should from the beginning give serious consideration to construction problems and pro-vide, in certain cases, complete instructions as well as methods for construction

1.2.2 General Considerations for the Design of Bridge Schemes

Factually, the structural design scheme of the bridge presents a complex problem for the structuraldesigner despite the presence of modern technology and advanced computer facilities The scope

of such a problem encompasses the determination of general dimensions of the structure, the spansystem (i.e., number and length of spans), the choice of a rational type of substructure Also, withinthis scope, there is a demand to find the most advantageous solution to the problem in order todetermine the maximum safety with minimum cost that is compatible with structural engineeringprinciples Fulfilling these demands will provide the proper solution to the technical and economicparameters, such as structure behavior, cost, safety, convenience, and external view

Also, during the design of a bridge, crossing the river should take into consideration the crosssection under the bridge that provides the required discharge of water The opening of the bridge

is measured from the level of high water as obtained at cross sections between piers, consideringthe configuration of the river channel, the coefficient of stream compression, and the permissibleerosion of the riverbed By changing the erosion coefficient and the cross-sectional area within thelimits permitted by the standards, it is possible to obtain different acceptable dimensions of openingsfor the same bridge crossing During the choice of the most expedient alternative, it is necessaryalso to consider that reducing the bridge opening is connected with increased cost of foundation

as a result of the large depth of erosion and the need to apply more-complicated and expensivestructures for stream flow During the design of such structures as viaducts and overpasses, theirtotal length is usually given, which may be determined by the general plan or by the landscape ofthe location and the relation of the cost of an embankment of great height and the bridge structure.The design of the bridge usually starts with the development of a series of possible alternatives

By comparing alternatives, considering technical and economic parameters, we try to find the mostexpedient solution for the local site conditions At the present time, the development and compar-ison of alternatives is the only way to find the most expedient solution Factors influencing thechoice of bridge scheme are various and their number is so great that obtaining a direct answer towhat bridge scheme is most rational at a given local condition is a challenge It is necessary todevelop a few alternatives based on local conditions (geologic, hydrologic, shipping, construction,etc.) and apply the creative initiative of the designer to the choice of a structural solution Providingstructural schemes of bridge alternatives is a creative act., computers can be used to determine the

most advantageous span length and span system, to find the number of girders on the bridge having

a top deck or the number of panels in the truss, and to choose the substructure However, usingcomputers to make a choice of rational alternatives, considering a comparison of all technical andeconomic parameters, is impossible Finding an optimum alternative using different points of viewoften leads to different conclusions For example, the alternative may be the most advantageous bycost, but may require great expenditure on metal or require special erection equipment, whichcannot be obtained Some alternatives may not satisfy an architectural requirement, when consid-ering city bridges When using computers it is still impossible to refute the conventional designmethod, considering all problems of specific local condition, which are practically impossible towrite into a computer program

1.2.3 Theoretical Basic Method of Preliminary Design

Methods of design cannot be invented on the basis of certain arbitrary principles They are developedfrom practice In a given theoretical study, there are enough proofs that methods of design arechanging depending upon the bridge-building practice and its basic problems Therefore, today’sapplied method of preliminary design is mainly determined by empirical methods

To achieve improvement, this method is based on consistency in its exact application and nation of its logical basis This advanced method of preliminary design makes it possible to develop

expla-a perfect finexpla-al solution for the project It is worth mentioning expla-at this point the importexpla-ance ofcalculation parameters in the considered design approach

Using mathematical models, it is possible to express (see Figure 1.1) the quality indexes U of thestructure as a function of its parameters; x, y, z, i.e.,

Preliminary design provides means to determine the exact values of parameters and their qualityindexes The problem is similar to finding the limit of a function, as in calculus of variation Thisanalogy may be used to determine a logical basis for the method of preliminary design It is clearthat the problem of preliminary design cannot be solved in pure mathematics The quality indexescannot be expressed by algebraic functions Note that the majority of parameters from one alter-

FIGURE 1.1 Quality index of the structure.

native to another change their size rapidly Alternatives are shown only for consideration and toshow the investigation process in order to prove the correctness of the accepted alternative.Only in particular cases can a mathematical method be applied to find the limit For instance, it

is known that by this method it is possible to find exact dimensions of span lengths of simple-spantrusses or exact heights of steel trusses those with parallel chords because of their behavior ofminimal total weight of the structure

To find the limit of the function U, it is possible to find the corresponding values of parameters

x, y, z from the following equation:

(1.2)

These equations provide the tool to investigate the influence of each parameter as it changes thequality indexes of the structure Leaving all other parameters constant, ±∆x is imposed to study thechange of the value U We can then find the value of the parameter for which ∆U changes its sign.This corresponds to the minimum of the function U

Note that the separate parameters are interrelated If one parameter is changed, it is necessary tomodify the others By exceeding certain limits, the span of the reinforced concrete bridge mustchange from a beam system to an arched system Applying this method of preliminary design tobridges, the comparison of Eq (1.2) leads to composition of alternatives For each equation in

Eq (1.2), it is necessary to use a minimum of three alternatives The first equation is formed fromcertain values of parameters x1, y1, z1, etc Leaving parameters y1 and z1 constant gives a new value

of x, which is x2 to compose a second alternative Comparing this with the first, we establish thechange of quality indexes of the bridge If they have improved, it is necessary to change again theparameter x in the same direction, raising it to the new value x3 to form a third alternative Then,

we compare this with the first two alternatives to determine the change of the quality indexes forthe designed bridge If, for example, they become worse, then their maximum value corresponds

to x2 (see Figure 1.1) If they improve, it is necessary to repeat the investigation for the secondequation ∂U/∂y = 0, and so on All these equations must be solved simultaneously In preliminarydesign, this means it is necessary to prepare many alternatives and compare them simultaneously.This process is difficult and tedious The difficulty is increased because, unlike the purely mathe-matical method where the function U is given, in preliminary design the type of function is notknown and should be determined

Because of the above-mentioned difficulties, there is enough ground to assume that the first stage

of the design process is based on creativity and invention

How to build a bridge over a certain river? There are number of different answers to this question.The type of bridge can be steel or reinforced concrete, and for each case there are a number ofapplicable alternatives If, for the given problem, there are several known solutions, there could bejust as many or more undeveloped This shows that building a bridge and creating a design are noteasy tasks Many undetermined problems face the designer However, engineering science has provedthat these difficulties could be solved in a systematic sequence, as illustrated below

1 Equation (1.2) should be applied to the problem of structural design and solved by a method

of successive approximations which follow preliminary design This method is considered to

be technically reliable and has been used in engineering successfully In order to improve andaccelerate this method (of successive approximation), it is of major importance to chooseabsolute precision Experience, in a significant way, helps in making such a decision

2 Preliminary design is generally the first approximation in the creation of a bridge project Itsolves the equation for the most important parameters which have great influence on thequality indexes of the structure Details of the structure may be investigated at a later stage

Many solutions have been developed in practice for detailed structure It is worth mentioningthat when working with parameters, there are not many basic ones.

3 Some parameters are given and remain constant during design Others take a limited number

of values and this shortens the number of alternatives Relations among the parameters, theircorrection, and the importance for the quality indexes of the bridge make it easier to carryout the methods of investigation of alternatives

If it were possible to solve the problem by pure mathematics, then the solution would be simply

to solve the equations But we should remember that these equations (except those of the firstdegree) have several roots and arbitrary constants In application to bridge design, this means, if afew equally valid alternatives are obtained, the investigation should be refined further

The method of successive approximations should be accepted as the methodological principlebecause, as the process results in several alternatives for one project, we should consider only thebest scientific solution We may stop at an approximate solution, but only after we have beenconvinced that, in comparison with other solutions, it is the best scientific approach This is thebest way to generate designer success The same method is applied for choosing a bridge system,

as well as making a final choice for the material of bridge design, and so on

1.2.4 Choice of Final Alternative for Reinforced-Concrete Bridges

The designer may, for instance, decide that, for a given material (say, reinforced concrete), a thirdalternative is chosen Using this reasoning, the following imperfection arises: in the mathematicalanalogy, it was necessary to solve Eq (1.2) simultaneously, but here each is solved separately Afterdetermining a certain parameter, it will be kept constant and the choice for the others will follow.There is an element of sensitivity within this method The values of parameters are not chosenarbitrarily The initial values are determined empirically so that their values are as exact as the realones The order of invention of individual parameters is also important First, the parameters thataffect the quality indexes of the structure most significantly are investigated Then, investigation forthe less important parameters follows

Remember, the span structure implies length of span but also requires determination of the type

of span structure, its form, its shape, its system, the varied types which could be uniform or unequalspan structures, or the number of spans

Within this method, the chosen alternative determines the system of span structure with mum weight and maximum economy and safety Now, a legitimate question may arise Does itmean that the chosen alternative with varied type of span design (including span length, shape,form, and type) can be considered the best choice for the bridge project with maximum economyand safety? Although the answer may sound controversial and theocratically inconsistent, it is not.The answer is factually yes! There is a reason for that Certain types of bridge projects requirestructures of various type of spans which represent economically and safely the least choice forbridge design For refining, continue investigation by the method of successive approximation.Note, when laying out spans for frame-beam bridges, an equal span system is often used because

mini-it provides maximum standardization of elements However, the application of unequal span struction is also possible and in certain cases more favorable

con-In following the above discussion, if an economically feasible span alternative is not satisfactory,say, does not meet the requirements of shipping regulations, or if the bridge length does not permitequal spans, then it is necessary by the method of successive approximation to find more sensitivealternative schemes with a system of spans unequal in shape, form, length, etc

In conclusion, by changing the span system, the number of spans, or their form or shape or theircombination or dimensions, it is possible to obtain a number of alternatives that will satisfy thebest given local conditions at minimum cost

For instance, changing the span system, say, by reducing the number of spans, results into areexamination of the whole bridge design, and consequently a new bridge scheme should be drafted

If the weight of the span structure is relieved, the span system should be modified either by decreasingthe span length or span shape or form or other aspects of span structure.

It worth mentioning at this point that the significance of choosing the right alternative for thespan system should not be underestimated This is because the choice of material type for the bridgestructure (e.g., monolith or prefabricated, conventional or prestressed, or reinforced concrete) is oflesser importance in cost value than the total span system, which consists of length, shape, form,number of spans, etc Due to the relative simplicity of reinforced concrete shapes of spans andsupports, calculating their volume is not a difficult process if their dimensions are given or deter-mined from preliminary calculations

The greatest advantage of applying theoretical methods is that the process of design is not abstractand is based on scientific analysis and quantifiable information Therefore, during the process ofchoosing the best alternatives for solution, there are opportunities for eliminating imperfectionsfor each scheme Typical for this method is searching for the best solution through detailed inves-tigation for each material, superstructure, bridge system, etc

The number of alternatives obtained could be large In the scheme of variation given in Table 1.2

it was decided to compose these alternatives with subalternatives It takes extensive investigation,which is not always necessary In some cases, shorter methods may be applied In the example shown

in Table 1.2, it is possible to choose the bridge material first, thus composing one alternative forsteel and one for reinforced concrete systems It is advisable to consider information from experienceusing an empirical approach for bridge schemes

Example 1.1: Preliminary Design of Highway Bridge

TABLE 1.1 Preliminary Design — Example 1

Design Stages Beam System

First alternative System of span structure, deck-type beam; bridge having three spans; construction

of span structure from reinforced concrete having four main beams; supports are massive

Second alternative Same, only two spans

Third alternative Same, only four spans

Comparison of alternatives The best alternative is four spans (third alternative); the first and second alternatives

are canceled Subalternatives of third alternative 1 Four-span alternative with two main beams and supports from third alternative

two columns

2 Same, with prestressed concrete

3 With application of welded reinforcing frame Comparison of alternatives The third alternative is chosen; four-span bridges with two main reinforced concrete

beams Fourth alternative Arch-type, three spans with four separate arches and columns above arches; supports

are massive Fifth alternative Same, two spans

Sixth alternative Same, four spans

Comparison of alternatives Fourth alternative is chosen: three-span bridge with four separate arches

Subalternatives of fourth alternative 1 With two narrow arches and walls above arches

2 With box-type arches Comparison of alternatives Fourth alternative is chosen: three-span bridges with four separate arches

existing available data in practice Thus, new investigations are unnecessary and this results insignificant savings in design analysis and endeavor.

1.3 Final Design

1.3.1 Basic Trends in the Design of Bridges

In many aspects, the design of bridges is based on exact analysis and for this reason it is analogous

to the solution of mathematical problems, where the results are obtained by examining the problemdata and utilizing mathematical methods to arrive at a solution This approach works well fortechnical and economic analyses which present very important aspects of bridge design, but it leavesout a significant part of the project

This is because, first of all, many problems cannot be solved numerically Second, the analysismay not correspond exactly to the actual situation Technical analysis is valid for providing infor-mation for construction, but not significant for the solution of basic problems: choice of bridgesystem, choice of material, general dimensions, foundation problems, etc These problems are solved

on the basis of general considerations and the designer’s judgment

For the same problems in technical analysis or basic problems, for a bridge project there could

be as many proposals as the number of the participating designers involved in engineering disputes[6] The final choice of alternative depends to some extent on the attending participants who defendtheir view and support their arguments technically It is necessary to analyze the different reasoningand determine which proposal is the most consistent with prevailing and accepted standards in thepresent circumstances

The assistance of different methodological trends in bridge design is inevitable consideringcenturies of steady improvement and progress in bridge engineering Progress in techniques ofbridge construction depends on scientific and technological developments at each historical moment

in the creation of a bridge; traditions are preserved and present views are formed

An investigation of the history of bridges demonstrates that bridge construction has passed throughseveral industrial stages [7] We can separate these stages into primitive, industrial, architectural, andengineering phases These can be subdivided still further into simpler forms and characteristics.The influence of previous centuries on bridge design indicates that, to best understand the presenttrends, one must study the evolution of bridge engineering Note that it reflects involvement ofmaterials, the spiritual culture of the society, and the transfer of heritage Concerning technological

TABLE 1.2 Preliminary Design — Example 2

Design Stages Beam System

First alternative Reinforced-concrete beam, three-span bridge of deck system, with four main beams;

supports are massive Second alternative Steel beams two spans

Comparison of alternatives The first alternative is chosen: reinforced-concrete bridge

Third alternative Reinforced-concrete arch, two spans having four separate arches

Comparison of alternatives After comparison of the first and third alternatives, the first alternative is chosen:

beam bridge Fourth alternative Two spans, reinforced-concrete beam bridge

Fifth alternative Four spans, reinforced-concrete beam bridge

Comparison of alternatives After comparison of the first, fourth, and fifth alternatives, the fifth alternative is

chosen: four-span bridge Subalternatives of fifth alternative 1 With two main beams, monolith

2 Same, with four beams, prestressed concrete prefabricated

3 Same, with welded reinforcing frame Comparison of alternatives By comparison of the fifth basic and additional alternatives, fifth subalternative 2

is chosen

advances universities have had a large influence The future engineers take from their professorsthe basic knowledge and new trends in design.

1.3.2 Creative Trends

In the 20th century, bridge design has undergone considerable change With increasing demand forreinforced-concrete bridges, the need for and the creation of a new system was inevitable The oldmethods had many limitations and will not be discussed here They actually presented manyobstacles for further developments in bridge engineering It was necessary to create new specifica-tions for reinforced-concrete structures

The construction of highway bridges and the application of reinforced concrete presented ers with a basic problem regarding the choice of the bridge system This created strong demand forpreliminary design This new concept required developing new methods and has put pressure ondesigners to look at the bridge not as a condensation of essential parts but rather as a monolithiccompound unit with interrelated parts

design-Because of the growing demand for reinforced-concrete and suspension bridges, the designer hadlarge choice of materials and means to develop new bridge systems and the idea of cable-stayedbridges followed The new century created strong demand for an analytical approach and necessi-tated a growing need for preliminary design with more schemes

The acceptance that for each case there is no one solution but, rather, that there are several fromwhich it is possible to choose the one most consistent with prevailing, accepted standards and mosteffective for the actual project leads to the basic characteristic of the second significant trend inbridge design, which will be called “creative.”

Therefore, the design of each bridge is a process of finding a solution to a new problem If there

is no solution available, it must be sought Considering the role of personal creation, this secondtrend may provide original new projects Supporters of such a trend believe that creation of a bridgedepends upon personal predisposition, capability, and vision Design is considered to be a creativeprocess that consists of a combination of structural expressions based on required knowledge andprofessional intuition

1.3.3 Practical Trends

Practicability is the main consideration in this trend The word practical goes hand in hand withscientific investigation using modern technology Designers use both scientific principles and cre-ativity for their designs only in order to solve the actual problem In this trend, the bridge isconsidered as part of the highway or railway and its basic purpose is to satisfy the requirements oftransportation

The bridge should satisfy the basic requirements of safety and economic factors The construction

of the bridge should also follow the pattern of successful industrial methods

Supporters of the creative trend considered highways and railways as areas to apply their creativecapabilities and for testing their new inventions Followers of scientific analysis investigation con-sidered highways as large laboratories for their investigations Adherents of practical design haveborrowed their concepts from both trends, insisting that bridges must be first safe and permittedexperimental structures only on secondary highways Practical designers suggested that the structureshould be standardized for industrial preparation because it could lead to faster ways of reconstruc-tion or rehabilitation Also, practical designers insist on use of construction techniques that requireminimum maintenance and do not affect the traffic flow

1.3.4 Basic Assumptions of Design

Methodological rules compatible with technical and applicable requirements in bridge engineeringplay a major role in modern progressive methods for designing bridges

Nowadays, time is an important factor, especially in bridge construction Progressive methodsmust satisfy technical swift performance as well as requirements of astute engineering economy.Such majestic structures must function effectively and, in addition, be aesthetically appealing.Bridges play the major role in the transportation system crossing rivers or other obstructions.

At different times, bridges were built for more than one purpose The following are examples:

1 Roman bridges and those built in the Middle Ages served not only for transportation or forchariots, but also for joyful, exuberant activities for the population These traditions werecontinued at later times

2 Another trend that appeared in the Middle Ages is the construction of bridges for fortresses,castles, and towers as a protective measure against attacks by enemies An example is thebridge at Avignon, France; also “London Tower Bridge,” which was built with towers foraesthetic purposes only

3 Another trend in the same era was to build chapels on bridges and to collect tolls to maintainthem, the same old problem of upkeep (e.g., Italy, Spain, Germany)

4 During the Middle Ages and later, bridges were built to serve as dams for water mills, whichwere important parts of the economy in those days (e.g., Holland)

5 During the 16th and 17th centuries bridges were built as wide structures for shops andconvenience in general Good examples are London Bridge, England and Ponte Vecchio,Florence, Italy Construction of these types of bridges was terminated toward the beginning

of the 19th century

6 In Western civilizations, bridges are sometimes built as majestic monuments to commemorateoutstanding events or achievements of national importance for an important person ornational hero Examples are the monument to George Washington, the George WashingtonBridge, New York City; the monument to Princess Margaret of Great Britain, The PrincessMargaret Bridge, Fredericton, New Brunswick, Canada (this bridge was designed by M S.Troitsky); the monument to the victory at the Battle of Waterloo, The Waterloo Bridge,London, England; the monument to Russian Tzar Alexander the Third, The Alexander IIIrdBridge, Paris, France (one of the most beautiful cast-iron bridges of imperial style); themonument of the Sarajevo Association, The Gavrilo Princip Bridge, Sarajevo, Yugoslavia; themonument to Napoleon Bonaparte’s victory at the battle of Austerlitz, Austerlitz Bridge,Austria

The 19th century was characterized by industrial growth, and the use of bridges was confined totransportation as a result of the boom in building railways Later, with Ford promoting “auto-vehicles,” the building of bridges for highways became in great demand This new trend in transportrequirements put on pressure to improve safety factors as well As a result, it is very important inmodern bridge engineering to determine the carrying capacity of the bridge or the maximum value

of the temporary vertical load that the bridge can bear

Also, to avoid interruption in traffic flow, the calculations should consider the maximum number

of vehicles passing in a given time For bridges crossing navigable rivers, passing clearance must beconsidered Also, similar consideration should be given to underpasses The carrying capacity of abridge is defined by the number of lanes, their width, and the accepted lateral clear distances ofshoulders and medians required for safety considerations

To avoid interrupted traffic flow, it is necessary for the width of the bridge to be greater thanthat required by the calculated carrying capacity For example, in long bridges, it is necessary toprovide an extra parking space for possible emergency cases in order to prevent a traffic jam As arule, the width of the roadway on the bridge is equal to the width of the highway However, theremay be deviations from this rule For instance, although the highway may accommodate three lanesfor traffic, the number of lanes on the bridge could be reduced Also, there are examples of thereversed situation

The condition of maximum traffic suitability and convenience is not a requirement but is ferred and attention should be paid to this issue during planning the project Also, this issue could

pre-be considered as one of the criteria for the appraisal of the project, provided that the cost is notprohibively excessive

The most efficient functional bridge structure is considered to be the one that embodies the mostrequirements of transport, with top safety factors, carrying capacity, that contains extra conveniencefacilities, that is most effective in labor and material, and that can be completed in a reasonabletime Since Henry Ford’s time, extra pressure has been put on the transportation system, primarily

on highways and railways, which has directly affected innovation in bridges Modern-day transport

is increasing in number and weight This means bridges must be designed so that their carryingand passing capacities can accommodate heavier vehicles and larger numbers of vehicles Designersmust be resourceful and have means to overcome difficult situations effectively and to cope withthe growing demands of faster and larger moving transport with the greater reserves for futuregrowth, the longer the bridge stands without needing repair or reinforcement

Note that by increasing the reserves for passing and carrying capacities, the cost of the bridgewill increase Determining the necessary reserve is a problem that needs to be resolved by engineeringeconomy The Romans did not visualize the fast development of transport and means for transpor-tation, but concentrated their conceptual design on timelessness of the bridge structure and, forthis purpose, provided great reserves for passing and carrying capacities

The property of material is not necessarily the basic factor that defines the service time and safety

of the bridge More often, bridges are reconstructed for other reasons: too small passing and carryingcapacity, insufficient clearance under the bridge, straightening of lanes or reduction of the grade

1.3.5 Basic Requirement of the Bridge under Design

Choosing the right location is crucial for designing and planning a bridge But above all, safetyconsiderations that govern the technical, functional, economic, efficiencies, expeditiousness, andaesthetic requirements are very important It is necessary for the bridge and each of its components

to be safe, durable, reliable, and stable This is usually checked by analysis using current tions But not all questions of durability, reliability, and stability may be answered by analysis.Therefore, in some cases it is necessary to provide special measures such as testing the performance

specifica-of the structure and examining its behavior under maximum loading on the construction site.Specifications and technical requirements should be satisfied because they guarantee the carryingcapacity of the structure From the safety point of view, all bridges designed according to thetechnical requirements are equal But practically speaking, different aspects of technical require-ments may be satisfied with different margins of safety

Regarding the various bridge components, it is necessary to know that for engineering structures,the best solution should provide the appropriate material and carrying capacity

During comparison of projects, the technical requirements should be considered Because technicalrequirements may be accomplished using alternatives, consideration should always be given to addi-tional guarantees for safety Never compromise the safety of the passengers Essential requirementsnaturally should have great importance, but they are basically satisfied by accepted clearance Also,additional consideration must be given to issues other than elementary demands in order to make trafficflow efficiently Note that the height of the bridge and the elevation of the roadway must be determined

at an early stage, because they have influence on the traffic flow Also, greater or smaller grades of theapproaches should be designed earlier in the project Maximum grades are defined by specifications,but for practical purposes minimum grades are the most convenient Further, it is important to definethe number of joints in the roadway that correlate to the division of the structure in separate sections.Conditions of minimum wear of the parts of carrying construction under the influence of movingvehicles are also important to consider Regarding the maintenance of the roadway and the bridge, it

is possible to consider this as a general expense and therefore relate it to economic considerations