Seismic safety evaluation of URM buildings through incremental dynamic analysis

Abstract

The complexity in modeling Un-Reinforced Masonry (URM) buildings to understand their behaviour under seismic loading has been recognised in literature. The main objective of this study is to identify a methodology for quantification of seismic safety of URM building through incremental dynamic analysis. Prathmic Swasthya Kendra a single storey hospital building constructed in 1960 located at Uttarakhand, India, has been considered for this study. In the present study, equivalent frame modeling procedure for URM building has been adopted. User-defined shear hinge and flexural hinge properties are developed and are used in the analysis. Fragility curves are developed for the URM building from the incremental dynamic analysis, wherein, uncertainty in the characteristics of earthquake time histories are accounted by the use of suite of far-field ground motions. Fragility curves for different performance levels similar to that of. Immediate Occupancy (IO), Life Safety (LS) and Collapse Prevention (CP) as specified in FEMA 356 (2000) have been developed and collapse margin ratio is estimated. Adjusted Collapse Margin Ratio (ACMR) has been evaluated and comparisons are made with the minimum acceptance criteria specified for collapse limit state. As a part of the methodology, response reduction factor (R) is obtained for the URM building and the comparison has been made with the respective specification for URM building specified in Indian seismic standard. The methodology proposed can be adopted for seismic safety evaluation of existing or new URM buildings.