Stiffness method for analysis of foundations using subgrade modulus

Analysis of foundations primarily requires the input from soil in two forms such as safe bearing capacity (SBC) and modulus of subgrade reaction of soil. When SBC is considered for analysis, the foundation is treated as rigid and when modulus of subgrade reaction is considered then the foundation is treated as flexible. It is usual that foundations for small structures are analyzed using SBC of soil but for large structures where economy plays an important role, the foundations can be analyzed with subgrade modulus reaction. When the column loads are high in soils with poor bearing capacity, raft foundations are preferred. In case of insufficient bearing area sometimes rafts are supported by piles. Sometimes, due to the poor bearing capacity of soil the foundations are difficult to analyze when raft foundations are supported by piles. In this paper an attempt is made to analyze the raft foundations resting on piles with the concept of subgrade modulus. Finite element is preferred for analysis of raft foundations with subgrade modulus. In the present work it is proposed to analyze the foundations using subgrade modulus theory with the help of stiffness method and will be compared with the finite element (FEM) software.