Effects Of Impact On The Seismic Response Of MSSS Bridges

This paper presents results of a study on the effect of impact on seismic response of Multi-Span Simply-Supported (MSSS) bridges. The investigation includes detailed dynamic analysis of three actual bridges as representatives of 2,3, and 4 span bridges, which are common in the Eastern United States. Furthermore, using a Stiffening Single-Degree-Of-Freedom (S-SDOF) model a series of parametric study are performed. The objectives are to better quanti~ the effect of impact on the seismic performance of MSSS bridges and to provide the knowledge base for development of design guidelines within a performancebased framework. Several damage criteria, namely displacemen~ dissipated hysteretic energy, and low-cycle fatigue darnage index are considered. It is shown that on the average displacement dem&ds are lower for S-SDOF systems, consistent with pushover analysis based on current seismic codes. However, considering other damage criteria, it is quite possible for an S-SDOF system to sustain more damage than an elastic-plastic system. Design implications and the needs for future research are also discussed.