Chapter 2 - Nonlinear Material Behavior of the Bridge Components

Abstract

Chapter 1 has provided a brief background on steel and steel-concrete composite bridges and reviewed recent developments reported in the literature related to the design and finite element modeling of the bridges. This chapter highlights the nonlinear material behavior of the main components of steel and steel-concrete composite bridges, comprising structural steel, concrete, reinforcement bars, shear connectors, bolts, and welds. Overall, this chapter aims to provide a useful background regarding the stress-strain curves of the different materials used in the bridges. Also, this chapter aims to highlight the important parameters required for finite element modeling. The definitions of yield stresses, ultimate stresses, maximum strains at failure, initial stiffness, and proportional limit stresses are presented in this chapter. This chapter enables beginners to understand the fundamental behavior of the materials in order to correctly insert them in the finite element analyses. Covering the behavior of shear connectors in this chapter is also important to understand how the shear forces are transmitted at the steel-concrete slab interfaces in composite bridges. In addition, the material properties of the main components of joints used in steel and steel-concrete composite bridges such as bolts are highlighted in this chapter. Furthermore, this chapter presents how the different materials are treated in current codes of practice and the design values specified in current codes of practice. This chapter paves the way for Chapters 3 and 4, which address the design and stability issues related to steel and steel-concrete composite bridges. It should be noted that bridge components, such as structural steels, concrete, and reinforcement steels, are used in bridge and building constructions. However, when presenting the material behavior of a component in this chapter, it is presented as it is used in bridges. As an example, structural steels used in bridges generally have more rigid performance requirements compared with steels used in buildings. Bridge steels have to perform in an outdoor environment with relatively large temperature changes, are subjected to excessive cyclic live loading, and are often exposed to corrosive environments. In addition, steels are required to meet strength and ductility requirements for all structural applications. However, bridge steels have to provide adequate service with respect to the additional fatigue and fracture limit state. They also have to provide enhanced atmospheric corrosion resistance in many applications where they are used with normal protective coatings. For these reasons, structural steels for bridges are required to have fracture toughness and often corrosion resistance that exceed general structural requirements in building constructions. Overall, the author aims that this chapter acts as a basis for designing and finite element modeling of steel and steel-concrete composite bridges.