Seismic Performance of 3-D Infilled and Bare Frame RC Building Models using Average Spectral Acceleration

Abstract

This study compares the performance of the bare and infilled frames of RC buildings based on incremental dynamic analysis (IDA) and fragility analysis in the Performance Based Earthquake Engineering framework. Inter story drift ratio (IDR), maximum inter-story drift ratio (MIDR) and absolute peak floor acceleration (PFA) are chosen as engineering demand parameters (EDPs). Comparing the response of such different frames is always problematic because of their very different dynamic characteristics, a feature that to ensure efficiency imposes selecting different sets of accelerograms for response assessment. To bypass this problem as common intensity measure for both types of frames we used here the spectral acceleration averaged in a period range (AvgSA) that include the first mode periods of both frames. We further derived fragility curves for six case study buildings of regular 4-, 5-, 6-, 8- and irregular 6-, and gravity designed 6-story buildings. Except for the gravity designed 6-story building, we observed that the infilled frame buildings have slightly better performance at less severe limit states. For the gravity designed building performance, however, ignoring URM infill walls resulted in un-conservative collapse capacity estimates. Finally, exploring the comparison of the PFA response of the bare and infilled frames for the 6 case study buildings confirms that significantly higher demands are to be expected for the latter, suggesting the necessity of accounting for the infills when performing detailed building-specific loss estimation analysis or designing acceleration sensitive equipment. Hence, it is recommended to account for the infill elements in both design and assessment procedure to ensure the safety of structural and nonstructural elements.