Nonlinear seismic analysis of bridge structures. foundation-soil representation and ground motion input

Abstract

This paper introduces a nonlinear approach to the modeling of foundations that was used in the seismic analysis of the existing San Diego-Coronado Bay Bridge. The work described herein is part of a seismic-retrofit project commissioned by the California Department of Transportation (Caltrans). The tall piers and relatively short pile embedments typical of the Coronado bridge make the nonlinear overturning behavior of the pile caps an important behavior to simulate in seismic analysis. Therefore, a procedure which makes use of conventional static condensation techniques combined with nonlinear overturning moment characterization was developed and employed. The paper describes this modeling methodology as it compares to more conventional foundation modeling and summarizes the impact of including foundation nonlinearity vs linearization.