Assessment of P-Delta Effect on High Rise Building with Outriggers and Belt Truss

Abstract

The behaviour of structures, when subjected to critical loads is a complex phenomenon and is basically dependent on the type of forces/loads acting on the structure, magnitude of force, direction etc. Generally, the analysis of buildings is done by using linear elastic methods, which is first order structural analysis. The first order analysis is performed by assuming small deflection behaviour where the resulting forces, moments and displacements take no account of the additional effect due to deformation of the structure under vertical loads prior to imposing lateral loads. In the traditional first order analysis of structures, the effects of change in the structure actions due to structure deformations are neglected. However, when a structure deforms, the applied loads may cause additional actions in the structure that are called second order or p-delta effects. P-delta effect is secondary effect on structure. It is also known as ‘Geometric nonlinearity effect’. As number of storey’s increases, P-delta effect becomes more important. In this study the P-delta effect on skyscraper is studied. Linear static analysis (without P-delta effect) and nonlinear static analysis (with P-delta effect) on high rise buildings having outrigger with belt truss is carried out. For the analysis G+55 composite skyscraper is modelled. Earthquake load is applied on model of structure as per IS-1893(2002) for zone II in ETABS software. Load combinations for analysis are set as per IS-456(2000). Bending moment of column, story displacement with and without P-delta effect is calculated and compared for both models.