Seismic Performance Evaluation of Residential Cum Commercial Infilled Building

Abstract

A linear analysis is inadequate in assessing the seismic demand of a structure under the severe earthquake condition; therefore, a nonlinear static pushover analysis is needed. A pushover analysis helps to identify critical members which are likely to reach their critical state during an earthquake. Therefore, it is necessary to pay proper attention during the design and detailing of the structure. Due to the presence of the infill wall, stiffness of the RC frame increases and it changes the frame action of the moment resisting frame to a truss action thereby affecting the seismic response of the structure. In the present study, G+7 Story commercial cum residential reinforced concrete building is considered for push over analysis. The building has a basement, tower room for a staircase and a machine room for an elevator at the roof top. The shops are located on the ground, first and second story, auditorium rooms on third and fourth story and residential apartment on the remaining floors. As an auditorium room needs column free space for functional requirements, therefore, these are provided with floating columns. Four types of building models are analyzed using push over analysis. Model 1 has no infill walls (conventional model) while models 2, 3 and 4 are created with red clay brick infill wall, hollow concrete block infill wall and AAC block infill wall respectively. An equivalent strut approach is used for the modeling of infill walls. The nonlinear static analysis is performed for the seismic evaluation assessment using ETABS v18 software.  A comparison is made between various models in terms of story displacement, story drift, base shear, performance point and plastic hinge state. The results reveal that the inclusion of infill walls causes a significant increase in the stiffness of the structure and, in turn, reduces story displacement and story drift significantly. The AAC block infill being lighter in weight shows better performance. The formation of plastic hinges developed in the models shows a few deficiencies in the structure which need to be retrofitted for enhancing strength.