COMPARISON OF VARIOUS RETROFITTING TECHNIQUES TO ENHANCE THE FOUNDATION CAPACITY OF AN EXISTING MULTI-STOREYED R.C. BUILDING

Abstract

Taller buildings are preferably considered so as to accommodate the increasing population. It is a solution to the shortage of land for building construction. Thus, storey extensions are an increase popular way to densify cities. In cases where there is a need to extend the existing building, it poses enormous risk because of the fact that they were constructed without considering the aspect of further extension. Foundation undergoes an increase in settlement due to augmented loads because of the addition of storeys. Generally, retrofitting codes have given little attention to retrofitting of foundations due to its complexity in construction. In this paper different methods to retrofit the foundation are discussed so as to reduce the settlement for the vertical extended structures. Enlarging the area of foundation, underpinning with four end bearing piles of varying dimensions and underpinning with a group of nine end bearing piles. The analysis showed that as the height of the building increased, the settlement of the foundation increased but the percentage increase in the settlement value decreased with each addition of storey. The percentage increase in the settlement values of the existing was more with the addition of one storey than with the addition of two storey. The method of enlarging the foundation reduced the settlement values by 20.23% in case for the addition of one storey and by 19.55% for the addition of two storeys. About 82.21% reduction in differential settlement value was obtained in case of using end bearing piles of size 300mm x 300mm, 85.7% due to piles of size 400mm x 400mm, 89.37% due to piles of size 500mm x 500mm and the maximum reduction of 92.74% in the case of group of nine underpinned piles. As the dimension of the underpinning pile augments, the stiffness of the pile increases therefore the settlement value decreased.