Evaluation of ductility factor for structures subjected to long period of vibration

Abstract

The response modification factor (R) in IS1893 [5] is a significant parameter in the analysis of seismic design of structure by means of non-linear response of a structure. This paper enumerates on determining the actual values of R factor for RC special moment resisting frame by performing detailed non-linear static pushover analysis for various 2D framed structures of special moment resisting frames. A parametric study has been carried out by varying the time period up to 4 of the structure and zone factor and the corresponding R values are obtained, which primarily depends on three other factors. From the detailed analysis, a relationship between response reduction factor, Time period, Zone (Rµ-T-Z) has been proposed. The results show that the values of R, given in the codes are pessimistic and hence, an optimistic value shall be adopted based on the analytical results. As an application, the values arrived from the proposed relationship is then compared with the values obtained from the structures analyzed.