Ehab Ellobody - Finite Element Analysis and Design of Steel and Steel-Concrete Composite Bridges

Steel-concrete composite bridges; Steel bridges; Railway and highway bridges; Finite element modeling; Design approach; Full-scale testing simulation

Steel and steel-concrete composite bridges are commonly used all over the world because they combine both magnificent esthetic 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 duration of road closures, which minimizes disruption around the area of construction. The flexibility of the 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. The 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 the 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.

Highway bridges made of RC slabs on top of the steel beams can be efficiently designed as composite bridges to get the most benefit from both the steel beams and concrete slabs. Steel-concrete composite bridges offer additional advantages to the aforementioned advantages of steel bridges. Compared to steel bridges, composite bridges provide higher strength, higher stiffness, higher ductility, higher resistance to seismic loadings, full usage of materials, and particularly higher fire resistance. However, these advantages are maintained, provided that the steel beams and concrete slabs are connected via shear connectors to transmit shear forces at the interface between the two components. This will ensure that the two components act together in resisting applied traffic loads on the bridges, which will result in significant increases in the allowable vehicular weight limitations, the ability to transport heavy industrial and construction equipment, and the possibility to issue overload permits for specialized overweight and oversized vehicles. One of the main advantages of having steel beams acting together with concrete slabs in composite bridges is that premature possible failures of the two separate components are eliminated. For example, one of the primary modes of failure for concrete bridges is cracking of the concrete slabs and beams in tension, while for the steel bridges, the possible modes of failure are the formation of plastic hinges and the buckling of webs or flanges. By having the steel beams work together with the concrete slab, the whole slab will be mainly subjected to compressive forces, which reduces the possibility of tensile cracking. On the other hand, the presence of the concrete slab on top of the steel beams eliminates the buckling of the top flange of the steel beams. The efficient design of steel-concrete composite bridges can ensure that both the steel beams and concrete slabs work together in resisting applied traffic loads until failure occurs in both components, preferably at the same time, to get the maximum benefit from both components.