Earthquake-Resisting System Optimization and Pushover Analysis in Seismic Design of Approach Spans of New South Park Bridge

This paper addresses the optimization of an earthquake-resisting system (ERS) and pushover analysis in design of the approach spans of the new South Park Bridge in Seattle, Washington. An appropriate ERS is desired in bridge design, and it involves the application of both pinned column hinges and plastic hinges in seismic analysis to properly allocate the internal forces among bridge substructure components. The approach to derive the ERS is discussed. Conventionally, the column hinge is often modeled as a pinned hinge in pushover analysis, corresponding to the modeling in seismic elastic and plastic hinging analyses. In this design, the column hinge was also modeled as a plastic hinge with limited moment capacity. This novel modeling not only improves the performance-based design but also leads to new insights into pushover analysis. Finally, the design of intermediate piers is presented.