Estimating Park-Ang Damage Index Using Equivalent Systems

Abstract eng:
The performance-based seismic design (PBSD) philosophy aims at achieving a reliable performance from a structure for a given seismic hazard. There are two primary concerns of PBSD – a proper quantification of the uncertainties associated in the whole design process, and a better characterization of the potential structural damage. A probabilistic seismic hazard analysis (PSHA) and the use of structural parameters better correlated to seismic damage are the preferred tools for seismic demand estimation as per PBSD. For the present work, the Park-Ang damage index is selected as the seismic damage measure since it is considered to be one of the most realistic measures of structural damage. Hazard response spectra (probabilistic or deterministic) are the most common mode of characterizing the seismic hazard at a site, and these spectra represent the demand on single degree oscillators. In order to use these spectra for estimating the demand on a multi-degree of freedom system (MDOF), an equivalent single degree of freedom (ESDOF) system-based method is proposed here. The proposed method is tested on three two-dimensional steel moment resisting frames under several ground motion scenarios. For each frame, demands, in terms of Park-Ang damage index, on the corresponding ESDOF system are obtained under different ground motion scenarios and are compared with the actual demands on the MDOF structure. The accuracy of the estimation is judged through bias factor statistics for these three buildings, and the variation of effectiveness of the procedure is studied. Finally, the prospective use of these bias factors in reliability based design of structures considering Park-Ang damage index is discussed.

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