STEEL BRIDGES PDF
Preview STEEL BRIDGES
STEEL BRIDGES METWALLY ABU-HAMD Head of Structural Engineering Dept Professor of Bridge and Steel Structures Faculty of Engineering, Cairo University Any part of this book may be reproduced by any means WITHOUT the written permission of the author. Preface ___________________________________________ Bridges have always fascinated people, be it a primitive bridge over a canal or one of the magnificent long span modern bridges. People built bridges to challenge nature where some obstacles like rivers, valleys, or traffic block the way they want to pass through. Our transportation system would not exist without bridges. Their existence allows million of people, cars, and trains to travel every day and everywhere they want to go. It is obvious that both our economy and our society could not function without the technology of bridge engineering. Bridge building is one of the difficult constructional endeavors that both attracts and challenges structural engineers. The design of such complex structures requires a great deal of knowledge and experience. Depending on the bridge span to be covered, several types of bridge systems exist. Examples of bridge systems are beam bridges for short and moderate spans, arch bridges for moderate spans, and cable stayed bridges and suspension bridges for long spans. This book covers the design of steel bridges in general with emphasis on bridge systems commonly used to cover short and moderate spans, namely plate girder bridges, box girder bridges, and truss bridges. The book is intended for senior year college students and practicing bridge engineers. The contents of the book are organized into two parts: the first four chapters cover the design of steel bridges in general while the other four chapters cover the design of specific bridge types. Chapter 1 describes the different structural systems of steel bridges. Chapter 2 presents the design loads on roadway and railway bridges. Chapter 3 presents the design considerations. Chapter 4 covers the design of roadway and railway bridge floor. Chapter 5 covers the design of plate girder bridges. Chapter 6 covers the design of composite plate girders. Chapter 7 covers the design of box girder bridges. Chapter 8 covers the design of truss bridges. The author hopes that this book will enable structural engineers to design and construct steel bridges with better safety and economy. Dr Metwally Abu-Hamd Professor of Steel and Bridge Structures Faculty of Engineering Cairo University Giza, 2007 CONTENTS ___________________________________________ 1: INTRODUCTION 1.1 GENERAL 2 1.2 TYPES OF BRIDGES 5 1.3 MATERIALS FOR BRIDGE CONSTRUCTION 20 2: DESIGN LOADS ON BRIDGES 2.1 INTRODUCTION 26 2.2 ROADWAY DESIGN LOADINGS 26 2.3 RAILWAY DESIGN LOADINGS 32 2.4 OTHER LOADS ON BRIDGES 36 3: DESIGN CONSIDERATIONS 3.1 DESIGN PHILOSOPHIES 42 3.2 ALLOWABLE STRESSES FOR STRUCTURAL STEEL 43 3.3 FATIGUE 65 3.4 ALLOWABLE STRESSES FOR WELDED JOINTS 106 3.5 ALLOWABLE STRESSES FOR BOLTED JOINTS 107 4: BRIDGE FLOORS 4.1 INTRODUCTION 116 4.2 STRUCTURAL SYSTEMS OF BRIDGE FLOORS 117 4.3 DESIGN CONSIDERATIONS 122 4.4 DESIGN EXAMPLES 125 5: PLATE GIRDER BRIDGES 5.1 INTRODUCTION 146 5.2 GENERAL DESIGN CONSIDERATIONS 148 5.3 INFLUENCE OF BUCKLING ON GIRDERS DESIGN 154 5.4 ACTUAL STRENGTH OF PLATE GIRDER ELEMENTS 173 5.5 FLANGE PLATE CURTAILMENT 181 5.6 DESIGN DETAILS 183 5.7 FLANGE-TO-WEB CONNECTION 183 5.8 STIFFENERS 187 5.9 SPLICES 194 5.9.4 DESIGN 200 5.10 BRIDGE BRACINGS 203 5.11 BRIDGE BEARINGS 208 5.12 DESIGN EXAMPLE 218 6: COMPOSITE PLATE GIRDER BRIDGES 6.1 GENERAL 240 6.2 COMPONENTS OF COMPOSITE GIRDERS 243 6.3 DESIGN CONSIDERATIONS 245 6.4 SHEAR CONNECTORS 257 7: BOX GIRDER BRIDGES 7.1 INTRODUCTION 276 7.2 CROSS SECTION ARRANGEMENTS 278 7.3 BEHAVIOR OF BOX GIRDER BRIDGES 282 7.4 EFFECT BENDING 284 7.5 EFFECT OF TORSION 291 7.6 DESIGN EXAMPLE 306 8: TRUSS BRIDGES 8.1 TRUSS TYPES & CHARACTERISTICS 312 8.2 DESIGN OF TRUSS MEMBERS 318 8.3 GENERAL DESIGN PRINCIPLES 320 8.4 DESIGN OF TRUSS MEMBERS 322 8.5 DESIGN OF TRUSS CONNECTIONS 329 Chapter 1: Introduction 1 CHAPTER INTRODUCTION Steel Bridges 1 CHAPTER INTRODUCTION 1.1 GENERAL 1.1.1 Historical Background People have always needed to transport themselves and their goods from one place to another. In early times, waterways were used wherever possible. Navigable waterways, however, do not always go in the direction desired or may not be always available. Therefore, it has been necessary to develop land transportation methods and means of crossing waterways and valleys. Roadway and railway development have therefore become an absolute necessity for economic development. The rapid economic development in Europe, USA, and Japan could not take place until land transportation was developed. Even today, one important factor that has caused many countries to lag behind in economic development is the lack of good land transportation systems. An important element of land transportation systems is the bridge. A bridge is a structure that carries a service (which may be highway or railway traffic, a footpath, public utilities, etc.) over an obstacle (which may be another road or railway, a river, a valley, etc.), and then transfers the loads from the service to the foundations at ground level. The history of bridge engineering, which began with stone and wooden structures in the first century BC, can be said to be the history of the evolution of civil engineering. It is not possible to date humanity’s conception and creation of the first bridge. Perhaps people derived the first concept in bridge building from nature. The idea of a bridge might have developed from a tree trunk that had fallen across a canal. Early bridges consisted of simple short spans of stone slabs or tree trunks. For longer spans, Chapter 1: Introduction 3 strands of bamboo or vine were hung between two trees across a stream to make a suspension bridge. The introduction of new materials – plain, reinforced, and pre-stressed concrete; cast iron; wrought iron; and steel – evolved gradually within the last two centuries. According to known records, the first use of iron in bridges was a chain bridge built in 1734 in Prussia. Concrete was first used in 1840 for a 12-m span bridge in France. Reinforced concrete was not used in bridge construction until the beginning of the twentieth century. Pre-stressed concrete was introduced in 1927. These developments, coupled with advances in structural engineering and construction technology, led to the introduction of different forms of bridges having increasingly longer spans and more load carrying capacities. 1.1.2 Bridge Components In Figure 1.1 the principal components of a bridge structure are shown. The two basic parts are: (1) the substructure; which includes the piers, the abutments and the U U foundations. (2) the superstructure; which consists of: U U a) the bridge deck, which supports the direct loads due to traffic and all the other permanent loads to which the structure is subjected. In roadway bridges it includes the deck slab, Fig. 1.1b. In railway bridges it includes the rails and sleepers, Fig. 1.1c b) the floor beams, which transmit loads from the bridge deck to the bridge main girders. They consist of longitudinal beams, called stringers, and transversal beams, called cross girders, Fig. 1.1c. c) the main girders, which transmit the bridge vertical loads to the supports. d) the bracings, which transmit lateral loads to the supports and also provide lateral stability to compression members in the bridge, Fig. 1.1b. The connection between the substructure and the superstructure is usually made through bearings. However, rigid connections between the piers (and sometimes the abutments) may be adopted, such as in frame bridges, Figs. 1.4a and 1.4b. Steel Bridges a) Bridge Elevation Bridge deck stringer main girder bracing b) Cross Section of a Roadway Bridge c) Cross Section of a Railway Bridge Fig. 1.1 Principal Components of a Bridge Structure
Description:The list of books you might like
