Influence of Lateral Load Patterns on the Seismic Performance of RC Bridges by Incremental Dynamic Analysis

Abstract

The incremental dynamic analysis (IDA) by the concept of equivalent single degree of freedom (ESDOF) is applied to the bridge structures in this study to observe the influence of a selection of two different lateral load patterns, i.e., 1^st model load pattern (1st) and Uniform acceleration load pattern (Unif), on the seismic behavior of the RC bridges under three ground motions generated corresponding with the design spectrum for the inner area of Bangkok, Thailand. Three different bridge’s column heights were considered in order to investigate the effect of the different substructure flexibilities on the accuracy of using IDA by ESDOF to evaluate the seismic behavior of the bridges. The results show that the different lateral load patterns influence the lateral capacity of the bridge especially when the rotational mass moment of inertia was considered. The different lateral capacities lead to different incremental dynamic analysis curves (IDA curves) and lead to differences in seismic performance. The IDA curves show that the ESDOF with lateral capacity from Unif gives a slightly stiffer seismic behavior than the nonlinear time history analysis of whole bridges while the ESDOF with lateral capacity from 1st gives significantly weaker IDA curves for the bridge with short column height. However, the effect of different lateral load patterns on the IDA curves decreases when the bridge’s column height increases.

Keywords: Incremental dynamic analysis; lateral load pattern; rc bridge; seismic performance.