Effect of soil-structure interaction on low to medium-rise steel frames through shake table experiments

Abstract

The present study investigates the effect of soil-structure interaction on the dynamic response of low to medium-rise steel-moment-resisting-frame (SMRF) structures supported by isolated shallow footings resting on loose dry Ganga sand bed. A series of shake table experiments is conducted on three-dimensional steel models of a 3-storey and a 6-storey building for this purpose. The model frames are placed in a laminar container filled with dry Ganga sand of 36% relative density and subjected to a number of base excitations. Further, the same structures are tested under the fixed base conditions (i.e., clamped with the base plates) in order to isolate the effect of soil-structure interaction. Various engineering demand parameters such as storey displacement, base moment and foundation rocking are emphasized. It is observed that SSI causes significant increase in the storey displacement and reduction in the base moment of the building. The roof displacement is observed to increase up to twice for the 3-storey structure and up to 37% for the 6-storey structure for structure being placed on the Ganga sand bed compared to its fixed-base position. On the contrary, a reduction in base moment up to 65% and 90% is observed due to SSI effect for the 3-storey and 6-storey structure, respectively. The energy dissipations due to rocking movement are estimated up to about 36% and 42.6% for the 3-storey and 6-storey structure, respectively.