Inelastic Seismic Displacement Amplification for Bridges: Dependence upon Various Intensity Measures

Abstract

Reasonably simple yet accurate estimation of inelastic displacement demands on bridges during strong ground shaking is a critical step in the structural design process. Current code methods rely on the equal displacement rule at long periods, with ductility-dependent amplification factors applied at short periods. The purpose of this study is to evaluate the validity of these current methods for bridges subjected to ground motions of varying duration. Three methods are employed: inelastic response history analysis, the substitute structure method, and a recent ground motion prediction model from the literature. Each method confirms the strong dependence of inelastic displacement amplification upon various intensity measures of ground shaking, while current methods from bridge design specifications do not account for this dependence.