Evaluation and selection of ground motion intensity measures for nonlinear seismic demand and fragility analysis of MDOF systems

Kadaş, Koray
In performance-based seismic design methodology, intensity measures are thought to be key parameters of ground motion records that relate the seismic hazard levels with the structural response or damage. Therefore, it is important to identify efficient intensity measures that are capable of reducing the variability in seismic demand predictions. There exist several simple-to-advanced scalar and vector ground motion intensity measures; however, the literature is limited in the number of comparative studies investigating the efficiency of these parameters, especially in the entire response range of structures. In order to compensate for such shortcoming, a comprehensive research study has been undertaken to identify the most efficient intensity measures that would correlate well with key engineering demand parameters of low- to relatively high-rise reinforced concrete frames. The study elaborates on the subject utilizing both single- and multi-degree-of-freedom systems. Based on the correlation performances of a long list of simple scalar intensity parameters, a manageable list of indices has been shortlisted on which alternative ground motion record subsets were formed. The more complex multi-degree-of-freedom systems were later analyzed under these alternative record subsets to investigate the efficiency of an expanded list of intensity measures covering more advanced scalar and vector indices as well. Besides, the sufficiency of these parameters with respect to moment magnitude and source-to-site distance were evaluated through statistical analyses. Based on the interpretations of this second stage evaluation which utilizes a regression equation-based statistical approach, the best candidates have been identified for the reinforced concrete systems examined. In the last part of the study, the effect of shortlisted intensity measures on the ground motion selection stage of fragility analyses has been examined. Eventually, recommendations on the number of bins and records in each bin have been made to obtain reliable fragility curves that would lead to sufficiently accurate loss estimations of seismic vulnerability studies.
Citation Formats
K. Kadaş, “Evaluation and selection of ground motion intensity measures for nonlinear seismic demand and fragility analysis of MDOF systems,” Ph.D. - Doctoral Program, Middle East Technical University, 2021.