PERFORMANCE OF FLAT SLAB SHEAR-WALL-CORE BUILDING UNDER SEISMIC LOADING

Abstract

In flat slab building, the concrete slab rests directly on the columns. This system is highly in demand these days especially in metro cities due to ease in construction, low floor to floor height requirement and space use flexibility. This system is well capable to resist all gravity loads safely but it becomes vulnerable to damages under seismic loading. Due to such incapability of this system to resist lateral loading safely, many building codes restrict its use, without any lateral load resisting clement, to zones of lower seismic vulnerability areas only In current study, performance of flat slab system with and without shear-wall-core (SWC) and effect of infills has been studied under different levels of seismic hazards as classified in IS-] 893-2002. The study of 6 models (4 models of 8 storey and 2 models of 12 storey )in DBE IV, DBEV, MCEIII, MCE IV is done .The flat slab buildings with SWC, considered in current study, have been designed as per IS 456-2000 and IS 13920-1993 for design basis earthquake (DBE) IV level of earthquake hazard. Nonlinear Static (pushover) analysis has been used for performance evaluation of these buildings. 3 D modelling has been done on SAP-2000 V14.2.2 software package. The response of 8 and 12 storey flat slab buildings without and with 2 number of shear-wall-cores having infills in X or Y direction under seismic loading has been investigated. For modeling of flat slab, explicit transverse torsional member approach and for shear-wall-core, finite element approach (nonlinear shell clement) has been used. Infills are modeled using continuum model. Provisions of FEMA-356, ATC-40 and ACI-3 18-05 have been appropriately used to define nonlinear hinge properties in slab and columns. On the basis of this study, it can be observed that flat slab structure doesn't behave like conventional framed structure. Flat slab mainly fail in punching shear mode of failure, which progressively leads to the collapse of the building. With the introduction of shear-wall-core and infills in flat slab building, its behavior under seismic loading improves significantly