Developing efficient scalar and vector intensity measures for IDA capacity estimation by incorporating elastic spectral shape information

Abstract

SUMMARY Scalar and vector Intensity Measures are developed for the efficient estimation of limit-state capacities through Incremental Dynamic Analysis (IDA) by exploiting the elastic spectral shape of individual records. IDA is a powerful analysis method that involves subjecting a structural model to several ground motion records, each scaled to multiple levels of intensity (measured by the Intensity Measure or IM ), thus producing curves of structural response parameterized by the IM on top of which limit-states can be defined and corresponding capacities can be calculated. When traditional IM s are used, such as the peak ground acceleration or the first-mode spectral acceleration, the IM -values of the capacities can display large record-to-record variability, forcing the use of many records to achieve reliable results. By using single optimal spectral values as well as vectors and scalar combinations of them on three multistory buildings significant dispersion reductions are realized. Furthermore, IDA is extended to vector IM s, resulting in intricate fractile IDA surfaces. The results reveal the most influential spectral regions/periods for each limit-state and building, illustrating the evolution of such periods as the seismic intensity and the structural response increase towards global collapse. The ordinates of the elastic spectrum and the spectral shape of each individual record are found to significantly influence the seismic performance and they are shown to provide promising candidates for highly efficient IM s. Copyright c ∞ 2005 John Wiley & Sons, Ltd.