Optimum Location of Curtailed Shear Walls in SMRF

Abstract

Earthquake is a force of nature that can neither be precluded nor predicted before its mechanism is already set in motion. What man can do is mitigate the damage and minimize casualties when earthquakes do hit the surface. The central idea of Earthquake Engineering is to first understand the origin of seismic waves that are causative of the destruction and havoc and then learn various methods and procedures that can enable structures to withstand earthquake forces and maintain operation after the natural calamity has passed. Reinforced cement concrete (RCC) framed structures combined with shear walls have been widely used to resist lateral forces caused by wind load and earthquakes in tall buildings. Shear walls impart greater strength as well stiffness in their own plane and hence are generally provided for full height of the frames. Under lateral load, the shear wall deflects essentially in flexural shape and the frame deflects in shear shape. For this reason, these components are forced to interact horizontally through the floor slabs. Consequently, the upper part of the shear wall could play a negative role and may lead to unreasonable design by introducing additional internal forces to the system. Hence arises the need to curtail shear walls to reduce these forces, so that the advantages of shear walls can be reaped without their inconveniences. The scope of the current work was to determine optimum location of RC shear walls in two models, plan 1 - 7x3 bays and plan 2 - 9x3 bays respectively, for 20 storey RCC-framed buildings, with shear walls being curtailed at various heights. Response spectrum analysis has been performed using standard package SAP2000, along with P-delta effects to more precisely capture the behaviour of the dual system. A comparison of different parameters like deflection and shear has been made and a polynomial expression deduced using Regression Analysis in MS Excel. The expression not only explains the current behaviour, but can even be used to roughly predict the behaviour of taller buildings.