Probabilistic seismic Assessment of RC buildings with considering the effect of soil structure interaction

In this paper, the seismic response of base-isolated and fixed-base concrete structures with soil-structure-interaction effect was investigated. The structures with 4, 8, and 12 stories with lead rubber bearing isolators on three types of soils including soft, medium, and firm soils as well as on rigid foundation modeled using OpenSees software v 2.5.0. The ACI 318-02 code was used to design of RC intermediate moment frames. The incremental dynamic analysis was performed to determine the structural response under six near field and six far-field earthquakes recorded with the same seismic parameters but with different stations. The inter-story drift ratio and failure probability for each level of damage (slight, moderate, extensive and complete) were calculated and the fragility curves for maximum inter-story drift in different levels of PGA were drawn. The results indicated that considering the soil-structure-interaction decreased the structural damage on both isolated and fixed base structures. Softening the soil under isolated structures resulted in increasing the median fragility acceleration in each level of damage. Furthermore, considering the soil-structure-interaction effect in the low-rise to medium-rise structures (4 and 8 story buildings) has a more significant effect on median fragility accelerations than high-rise buildings. While, the effect of the base shear on the 12-story frame was more considerable.