Open ground story in properly designed reinforced concrete frame buildings with shear walls

Abstract

The effects of infill walls on the seismic response of reinforced concrete buildings and possible deficiencies caused by these members have been the subject of many research studies in the past decade. The open ground story where the infill walls are not present only in that particular story has generally been related to a soft-story deficiency. However, the formation of a soft story deficiency due to open ground story, or at least the scale of it may depend on certain properties of the building, infill wall and even characteristics of the ground motion. For instance, the existence of shear walls may not only change the overall structural behavior but also the contribution of masonry infill walls to the lateral response. In this study, reinforced concrete buildings which were designed according to the current seismic code previsions so as to contain varying amounts of shear walls are considered. It was aimed to concentrate on the soft story problem which may be induced by the non-uniform distribution of infill walls in these buildings with a special emphasis on the effect of shear walls. The nonlinear structural models without infills/with different patterns of infills were subjected to five different time-history records for this purpose. The results demonstrate that the existence of shear walls reduces the risk for a soft-story formation due to open ground story considerably. And there seems to be a critical value for the amount of shear walls in order to provide a meaningful reduction of this risk.