Seismic response analysis of RC framed buildings on geo-reinforced soil

Geotechnical seismic isolation is a recently emerged isolation technique to prevent the damaging effects of the earthquake on the building structures and nonstructural components. The study analyzes the effectiveness of different materials such as epoxy polystyrene, polyethylene foam, coir mat, rubber mat, and coir composites as a soil isolation medium to reduce the seismic energy transferred, thereby reducing the dynamic response of buildings under earthquake loads. Finite element analysis was carried out to evaluate the soil-structure interaction (SSI) effect in low-rise reinforced concrete structures with raft foundations subjected to various earthquake motions. Two kinds of soil, namely soft and stiff soil, were considered based on their flexibility to study dynamic soil-structure interaction effects. Roof acceleration and base shear of the building and contact pressure distribution and settlement at raft foundation-soil interface were the parameters evaluated for the different soil properties. The linear elastic behavior was assumed for the integrated building-foundation-soil system. This system was exposed to ground motions corresponding to scaled El Centro (1940) earthquake and simulated seismic excitation, which corresponds to the elastic design spectrum for Zone III as per the Indian standard code (IS 1893 (Part 1): 2016). The results indicate that the soil isolation provided by the high stiff polyethylene foam and coir mat substantially reduced the earthquake energy transmission to the superstructure. It is also observed that the seismic response of the buildings and raft is dependent on the flexibility of underlying soil. Seismic responses increase as the soil flexibility increases. Compared to stiff soil, the reinforced materials are very efficient in reducing seismic responses in soft soil.