Study of Loss of Contact for Rectangular Footings Resting on Soil

Abstract

Urbanization with its advantages has been constantly attracting people towards towns and cities. Land availability for providing facilities for residential and commercial activities has become a major problem. The engineering solution to this crisis has been addressed through the construction of multistoreyed buildings. Conventional structural design methods neglect the Soil-structure interaction (SSI) effects which is the major concern for risks. The differential settlements and underestimation of foundation pressure are the negative effects of SSI which are to be addressed for urban disaster risk management. In this aspect, an attempt is made in this paper to address some of the issues related to SSI. To quantify the parameters influencing the SSI, A Rectangular footing with L/B (Plan dimensions L, B) Ratios varying from 1.2 to 2 is modeled in ANSYS using SHELL63 elements. The SHELL63 element is capable of modeling the soil underneath the footing. The loss of contact of footing with soil is quantified by Relative Rigidity (RR) and Critical Relative Rigidity (CRR). The analysis is carried out by varying the eccentricity of concentrated load, plan dimension ratio and the Poisson’s ratio of soil. It is found that, as eccentricity of concentrated load increases the CRR decreases from 77 to 81%, for a particular L/B Ratio and Poisson’s ratio of footing. As the poisons ratio µ increases the CRR value decreases from 6 to 8%, for a particular L/B ratio of footing.