In this study, a series of experimental shaking table tests were performed on a physical fixed based model (structure directly fixed on top of the shaking table) and a flexible base model (soil-structure system) under the influence of four scaled earthquake acceleration records (two near field and two far field records) and the results were measured. The soil-structure system includes a 15 storey structural model resting on a synthetic clayey soil mixture consisting of kaolinite, bentonite, class F fly ash, lime, and water. The selected soil model was placed into a laminar soil container, designed and constructed to realistically simulate the free field conditions in shaking table tests. Comparing the measured response of fixed base and flexible base models, it is noted that the lateral deflections of flexible base model have evidently amplified in comparison to the fixed base model. As a result, performance level of the structural model may change extensively (e.g. from life safe to near collapse level), which may be extremely dangerous and safety threatening. Thus, it is experimentally observed that dynamic soil-structure interaction plays a significant role in seismic behaviour of moment resisting building frames resting on relatively soft soil
