Parametric Study of Raft Foundation for Multi-Storey Building with Different Structural System and for Varying Sub-Soil Condition

Sub structure is an important part of any multi-storey building as it gives stability to the super-structure. Foundation is designed as per the reactions coming from the super structure. Therefore, as the structural system changes, base reactions are changed and it affects the foundation design. The varying sub-soil conditions also affect the foundation. In this study, analysis and design of raft foundation is done in SAFE 2012 for multi-storey (G+10, G+15 and G+20) buildings with different structural systems and for different sub-soil conditions and comparison has been made. Here, three types of structural systems - simple frame, frame with shear wall and frame with bracing and three types of sub-soils - soft (k = 15000 kN/m3, N<10), medium (k = 40000 kN/m3, 1030) have been taken. By the comparative study, we have concluded that for the frame with shear wall, the cost of foundation is maximum than other two systems. For frame with bracing, the cost is more than that of simple frame. Also, the cost of foundation increases as soil changes from hard to soft. For soft soil, the soil pressure is exceeding the limiting value so in that case, raft foundation is not possible.