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(T 1 ), 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(T 1 ) is more efficient than other existing IMs. Further research will focus on the area-based IM involving higher modes of the structures.

An area‐based intensity measure for incremental dynamic analysis under two‐dimensional ground motion input

“…The main conclusions are listed as follows: IMs based on the ground motion in one direction are not suitable for IDA under two‐dimensional ground motion input any more. Combinational IMs should be adopted to consider the information on the ground motion in secondary direction. IMs with multivalues of spectral acceleration have more advantage in efficiency under two‐dimensional ground motion input. The area‐based IM A ( T 1 ), which was proposed by Zhou and Li, with a combination by the SRSS method is the most efficient for IDA under two‐dimensional ground motion input. In addition, A ( T 1 ) was proved to be efficient for IDA under one‐dimensional ground motion input in previous study .…”

“…As the area‐based IM A ( T 1 ) has been proved to be efficient for reinforced concrete frames under one‐dimensional ground motion input by Zhou and Li, the goal of this paper is to study the efficiency of the A ( T 1 ) and investigate the desirable combinational form of IMs under two‐dimensional ground motion input. Other six IMs in previous studies were combined into the three types and discussed here for comparison.…”

“…T m is suggested to be the period where the cumulative modal mass participation exceeds 95%.This parameter takes into account the effect of higher modes and nonlinearity simultaneously, but it is convinced that IMs that consider the higher modes effect fail to perform well to the first mode dominated structures. Thus, Zhou and Li proposed an improved area‐based IM A ( T 1 ), which is the area at the interval [ T 1 , 2 T 1 ] under acceleration spectrum for the first‐mode dominated structures. 2 T 1 was chosen as the integral boundary of the parameter on the basis of the experience of shaking table tests, which indicated that when the fundamental period of a structure reached 2 T 1 , the structure tended to be collapse.…”

“…2 T 1 was chosen as the integral boundary of the parameter on the basis of the experience of shaking table tests, which indicated that when the fundamental period of a structure reached 2 T 1 , the structure tended to be collapse. A ( T 1 ) has been proved more efficient than other IMs mentioned above for lower structures under one‐dimensional ground motion input by Zhou and Li . The efficiency of IMs above is mostly measured by IDA performed under one‐dimensional ground motion input.…”

“…And the combinational form of the IM and EDP should be proposed. As the superioty of the IM A ( T 1 ) to the first‐mode dominated structures has been proved, this paper is a further study that aims to prove the efficiency and desirable combination of the IM under two‐dimension ground motion input.…”