Abstract

Open ground storey (OGS) buildings are buildings on stilt floors which provide for vehicle parking space in the ground floor. Such buildings where the mass and stiffness is not uniform are called irregular buildings and are known to perform poorly under seismic loading. As a result the Indian code for evaluating earthquake loads on buildings penalizes these buildings by requiring their ground storey to be designed for two-and-a-half times the estimated base shear for a similar non-open ground storey building with no conditions on required stiffness. However, this may lead to undesirable performance because the ground storey columns are likely to get heavily reinforced and as a consequence have reduced levels of ductility. Also, since most of the lateral deformation of the building is likely to be concentrated at the ground storey, the storey drift is likely to exceed the stipulated values even under minor or moderate earthquakes thus causing performance problems. Open Storey is one of the main reasons for building damage during an earthquake and has been mentioned in all investigation report. Open Storey due to increase storey height is well known subject. Change in amount infill walls between stories also results in open story. These are usually not considered as a part of load bearing system. This study investigates the open storey behaviour due to lack of infills at ground floor storey and existence of this case by means of linear static and nonlinear static analysis for midrise reinforced concrete building. Open storey behaviour due to change in infill’s amount is evaluated in view of the displacement, drift demand and structural behaviour