Effects of Abutment's Modeling and Assignment of Plastic Hinge's Types on Seismic Response of Reinforced Concrete Highway Bridges

In seismic analysis and modeling of bridges، some assumptions are usually considered to simplify the analyses. Sometimes، these simplifications will cause some changes in seismic response of bridges. One of the important cases in this category is simplification of abutment’s modeling and assignment of different types of plastic hinges. Using simple and complex models of abutment in bridges is always an important factor in design and seismic response of bridges. Bridges with simple spans and continuous slab are commonly used in Iran. Therefore، the effects of three types of abutment models and plastic hinges on six bridges with various lengths and heights are analyzed. The bridges have the span of 20m and 5. 3-10m heights and have been studied with 3D models. Then، analyses are accomplished with modal، pushover and study of performance point of bridges using ATC-40 method. In this paper، abutments have been analyzed with roller، simple and complete types of modeling based on laboratory results. Simple modeling considers neoprene behavior and complete modeling is composed of neoprene، shear key، end wall and wing wall specifications. Results have been presented as mode shapes، maximum base shear and the performance level in the direction of longitudinal، transverse and the angle of 45° according to the principle direction. The difference between results is increased for bridges up to 80m total length. Therefore، in seismic analysis، the connivance of nonlinear behavior of abutment element will cause notable errors in results. However، for longer bridges the responses are too closed with consideration of three models. According to this fact that the studied bridges are the commonly used bridges in Iran، results of this study are applicable for designing، modeling and seismic analysis of bridges with simple spans and continuous slab.