Chapter 1 - Introduction

Abstract

Steel and steel-concrete composite bridges are commonly used all over the world, owing to the fact that they combine both magnificent aesthetic appearance and efficient structural competence. Their construction in a country not only resembles the vision and inspiration of their architects but also represents the country's existing development and dream of a better future. Compared to traditional reinforced concrete (RC) bridges, steel bridges offer many advantages, comprising high strength-to-self weight ratio, speed of construction, flexibility of construction, flexibility to modify, repair and recycle, durability, and artistic appearance. The high strength-to-self weight ratio of steel bridges minimizes dead loads of the bridges, which is particularly beneficial in poor ground conditions. Also, the high strength-to-self weight ratio of steel bridges makes it easy to transport, handle, and erect the bridge components. In addition, it facilitates very shallow construction depths, which overcome problems with headroom and flood clearances, and minimizes the length of approach ramps. Furthermore, high strength-to-self weight ratio of steel bridges permits the erection of large components, and in special circumstances, complete bridges may be installed in quite short periods. The speed of construction of steel bridges is attributed to the fact that most of the bridge components can be prefabricated and transported to the construction field, which reduces working time in hostile environments. The speed of construction of steel bridges also reduces the durations of road closures, which minimizes disruption around the area of construction. Flexibility of construction of steel bridges is attributed to the fact that the bridges can be constructed and installed using different methods and techniques. Installation may be conducted by cranes, launching, slide-in techniques, or transporters. Steel bridges give contractors the flexibility in terms of erection sequence and program. The bridge components can be sized to suit access restrictions at the site, and once erected, the steel girders provide a platform for subsequent operations. Flexibility to modify, repair, and recycle steel bridges is a result of the ability to modify the current status of the bridges such as widening the bridges to accommodate more lanes of traffic. Also, steel bridges can be repaired or strengthened by adding steel plates or advanced composite laminates to carry more traffic loads. In addition, if for any reason, such as end of their life of use or change of environment around the area, steel bridges can be recycled. Steel bridges are durable bridges, provided that they are well designed, properly maintained, and carefully protected against corrosion. Finally, steel bridges can fit most of the complex architecture designs, which in some cases are impossible to accommodate using traditional RC bridges.