Soil Structure Interaction of Framed Structure Supported on Soils of Different Stiffness

Abstract

Conventionally the design of a building is done considering fixed base supports. However, the supporting soil medium provides a certain degree of flexibility to the base which allows some movement of the foundation. When this happens, due to the flexibility provided by the soil, the natural period of the building frame will increase. An increase in the natural time period of the building may lead to increase in spectral acceleration. This is found to be true particularly for low rise buildings. In the present study we have considered building frames with isolated footing to check the changes in response when seismic loading is acting upon it. For this soil of different stiffness has been considered and different heights of buildings has been taken. The soil structure interaction (SSI) is an interaction between the soil and the structure which can used to study the response of the structure under seismic loads. The graphs between spectral acceleration and time period have been generated artificially using simulations on software. Our study shows that the effect of the soil structure interaction (SSI) will have a detrimental effect for low rise buildings, although for high rise buildings SSI will have beneficial effect. Therefore SSI has to be considered on case to case basis and no direct relation can be drawn. Still it can be concluded that for low rise buildings i.e. for buildings having stories less than ten, SSI should be carefully taken into consideration during design and it may be neglected for high rise building i.e. for buildings having stories greater than twenty.