Ductility reduction factors for masonry-Infilled reinforced concrete frames

Abstract

Masonry infilled RC frames are popular structural systems; however, there is lot of uncertainty in their response under seismic loads. Using the data from past experimental studies, a simple force-deformation model with three control points was developed. Effect of the model parameters was examined on ductility reduction factors (DRFs) and ductility demands (DDs). Statistical tests indicated that the ratio of the residual strength to the peak strength was the most significant parameter. The traditional approach of determining DRF ordinates through iteration for an assumed value of ductility may result in inappropriate values of DRF due to non-monotonic relationship between DRF and DD. Constant ductility charts were developed appropriately accounting for the non-monotonicity. It was found that the allowable DRF may be much higher if relatively weaker infill compared to the frame is used, which underscores the need for modification in codal provisions as they allow relatively stronger infill.