The major reasons of structures failure during earthquakes are Irregularities. Damages from earthquake generally initiates at locations of structural weaknesses in multistoreyed framed buildings. Buildings with openings in slabs are subjected to damages due to the action of lateral loads. Floor and roof systems act as horizontal diaphragms in building structures. They collect and transmit inertia forces to the vertical elements of lateral load resistant systems, i.e. columns and structural

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... . They also ensure that vertical components act together under gravity and seismic loads. Diaphragm openings are provided for the purpose of stairways, architectural features or shafts. In this works, openings in slabs are provided at various locations such as centre, at corners and at periphery with buildings having various shaped columns. The effects of size of openings in slabs were investigated. The seismic performance of multistory regular building is determined by Response Spectrum analysis in ETABS software