Effectiveness of Lateral Load Resisting Systems for Open Ground+20 Storied RC Framed Structure

Abstract

Abstract: In a highly populated country like India, problem of parking of the vehicles arises, this problem leaves no option for design of open ground storey buildings. Since there are no infill walls in ground storey, stiffness in the upper storey is much more than the ground storey. The columns in the ground storey are heavily stressed, therefore it is required that the ground storey columns must have sufficient strength and adequate ductility, the increased base shear is resisted entirely by the columns of ground storey only. These buildings are vulnerable due to the sudden lowering of stiffness and strength in the ground storey. This results in the attraction of more earthquake forces for the lower time periods, which also results in snapping of lateral ties in column, crushing of core concrete, buckling of longitudinal bars and finally shear failure in open ground storey columns due to lateral earthquake forces. Solution for this problem is to prevent the failure of open ground storey columns due to lateral earthquake forces by providing the lateral load resisting system. Many times, stiffness of walls is not considered while designing, this results in inaccurate designing of elements. An Open Ground +20 storied RC frame subjected to strong motion earthquakes viz. Duzce in Turkey (12/11/1999), Erzincan in Turkey (13/03/1992), Imperial valley at El-centro (19/05/1940), Landers (28/06/1992) and Nahanni in Canada (23/12/1985) creating soft storey effect at ground storey so it should be provided with lateral load resisting systems viz, Shear wall, steel bracing, lead rubber bearing base isolator with different configurations. Performance of equivalent diagonal strut provided to structure is compared with brick work modelled as actual brick work, equivalent diagonal struts, and considering only the mass of brick work. Time History Analysis is used in a RC framed building using ETABS Version18 and SAP2000 Version20 software in comparison with Response quantities Roof displacement, soft storey check, Base shear, overturning moment and storey drift. In this research, equivalent diagonal struts are provided as brick masonary, which shows accurate behavior of structure under strong ground motions as mass and stiffness both are considered during analysis. When Open ground storied structure is subjected to strong ground motions, stiffness at ground storey is drastically reduced. When structure is assigned with Lateral Load Resisting Systems, shear wall with configuration shear wall at ground storey and 1st storey, stiffness at ground storey is increased to 81% and 82% in X and Y direction respectively within permissible limits. Hence it can be concluded that when there is soft storey effect at open ground, structure becomes hazardous in presence of strong ground motions. When structure is subjected to strong ground motions, the vulnerability condition is high. Since we have performed non-linear dynamic time history analysis, more accurate results can be obtained as non-linear analysis considers vertical irregularities