Comparison of seismic vulnerability of buildings designed for higher force versus higher ductility

Abstract

Seismic vulnerability assessment is a complex problem involving input from various analyses. Pushover analysis is a commonly used method, which provides input for vulnerability analysis. Different level of ductility in a building can be considered by using different response reduction factor in linear analysis; however, the actual non-linear behavior of the building cannot be predicted on same basis. Therefore, response reduction factor (R) considered in designing, plays an important role in actual performance of building. The effect of different response reduction factors used in design on expected damage of building has been ascertained using vulnerability analysis. The seismic performance of low-rise and midrise RC buildings designed as per Indian codes with consideration of seismic forces (with two sets design levels SMRF and OMRF) and only gravity forces (designed for only gravity loadings) have been evaluated by fragility relationships. Nonlinear static analyses were performed to derive the fragility relationships. Based on nonlinear static procedure or pushover analysis the seismic performances in terms of ductility capacity and ductility demand have been obtained. The observations showed that the performance of buildings designed for higher ductility (R as 5) can be better relied than the buildings designed for higher forces (R as 3). The results showed that there is higher probability of damage in case of OMRF design buildings as compared to SMRF designed buildings.