An Area-based Intensity Measure for Incremental Dynamic Analysis

Abstract

Incremental Dynamic Analysis (IDA) is a parametric analysis method based on nonlinear dynamic analysis. It involves performing nonlinear dynamic analysis of the structural model to a suite of ground motion records, each scaled to multiple levels of intensity (as measured by Intensity Measure, IM), and recording the responses (measured by Engineering Demand Parameter, EDP). An IDA curve combines the intensity measure of a site-specific ground motion with structural responses from nonlinear dynamic analysis of the given structure. It is thus an unavoidable fact that the IDA curves display large record-to-record variability. This observed dispersion relies closely on the IM used. In other words, different IMs can lead to various results from the IDA method. The aim of this paper is to find a proper IM with an advantage in efficiency for IDA analysis. An area-based IM, A(T1), which considers the period elongation due to nonlinear deformation was proposed. A 6-story reinforced concrete frame was modeled to compare the efficiency of the proposed IM with existing IMs. It is concluded that IMs which consider the higher modes effect fail to perform well due to the domination of the first mode of the frame. Taking nonlinearity development into consideration, A(T1) is more efficient than other existing IMs. Further research will focus on the area-based IM involving higher modes of the structures.