EFFECT OF FOUNDATION SETTLEMENT AND ITS CONTROL IN MULTI-STOREYED R.C. FRAMED BUILDING

Abstract

Settlement of foundation can cause large strains and stresses in a structure. There is no detrimental effect in the structure if the footings settle by the same amount. However ,unequal settlements lead to stresses, deformations, cracks and even failure. The problem of estimating the differential .settlement becomes difficult due to the non-homogeneity of the natural soil deposits and the ability of the structure to bridge over soft spots in the subgrade. In the present study, a two bay frame with different number of storeys has been analysed under dead and live loads. Different soil conditions have been simulated with the help of spring constants. The frames have been provided with a foundation beam or a combination of plinth and foundation beams to study the decrease in magnitude of differential settlements and the corresponding change in the bending moments in beams and coulmns of the structure. Commercial software package STAAD-III has been used in the present study. Provision of foundation/plinth beam is effective in substantially reducing the differential settlement between two adjacent footings. With increase in stiffness of the foundation beam , the reduction in the bending moment in the upper storey beams and coulmns also increases. Similar trends have been observed with the combination of plinth and foundation beams.