Performance Based Seismic Design of RC Buildings Using SAP2000

Abstract

Earthquakes are one of the natural hazards that have potential to cause the maximum damages. These ground shaking forces are random and unpredictable in nature. Performance based design has gained a new dimension in the seismic design philosophy wherein the near field ground motion (usually acceleration) is considered. Earthquake loads are carefully modeled so as to assess the real behavior of structure with a clear understanding that damage is expected but it should be regulated. The recent advent of performance based design has brought the nonlinear static pushover analysis procedure to the forefront. Pushover analysis is a static nonlinear procedure in which the magnitude of the structural loading is incrementally increased in accordance with a certain predefined pattern. With the increase in the magnitude of the loading, weak links and failure modes of the structure are identified. The loading is monotonic with the effects of the cyclic behavior and load reversals being estimated by using a modified monotonic force deformation criteria and with damping approximations. Static pushover analysis is an attempt by the structural engineering profession to evaluate the real strength of the structure and it promises to be a useful and effective tool for performance based design. This study focuses on performance based design of three multistory RC framed buildings of Blue Area Islamabad, Pakistan, subjecting them to monotonically increasing lateral forces with an invariant height wise distribution until the preset performance level (target displacement) is reached. Considering the deficiencies indicated in analysis, these buildings were redesigned by adopting retrofitting techniques such as shear wall, bracing and column strengthening. These techniques strengthened structures to reach the targeted performance level.