Conventional analyses of structures are generally carried out by assuming the base of structures to be fixed. However, the soil below foundation alters the earthquake loading and varies the lateral forces acting on structure. Therefore, it is unrealistic to analyse the structure by considering it to be fixed at base. Multistorey reinforced concrete framed buildings of different heights with and without shear wall supported on raft foundation incorporating the effect of soil flexibility are considered in present study to investigate the differences in spectral acceleration coefficient , base shear, and storey shear obtained following the seismic provisions of Indian standard code and European code. Study shows that the value of base shear obtained for symmetric plan building is lowest in buildings with shear wall at all the four corners. 1. Introduction Common practice of analysis and design of buildings is to assume the base of building to be fixed, whereas in reality supporting soil influences the structural response by permitting movement to some extent due to its natural ability to deform. The lessons learned from past earthquakes of neglecting the effect of soil showed the importance of considering soil-structure interaction in the seismic analysis of structures. The action in which the response of the soil influences the motion of the structure and the motion of the structure influences the response of the soil is known as soil-structure interaction (SSI). Applying soil-structure interaction effects enables the designer to evaluate the real displacements of the soil-structure system precisely under seismic motion. The seismic response of structures due to the effect of soil flexibility depends on both the soil property and structure property. In seismic design of buildings, the consequences of soil flexibility are generally ignored. Mylonakis et al. [1] and Roy and Dutta [2, 3] showed the possible severities of neglecting the effects of the SSI in their studies. Similar study on implication of neglecting the SSI in ensuring the structural safety by conventional elastic and inelastic design procedure of moment-resisting building frames was shown by Tabatabaiefar et al. [4]. The effect of soil flexibility causing lengthening of lateral natural period in buildings due to lessening of lateral stiffness was reported by Bielak [5] and Stewart et al. [6, 7]. They reported that seismic responses of the buildings are altered by lengthening of lateral natural period, making it an important issue from the view-point of design considerations. Bhattacharya and
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