As an alternative to the very time consuming Non-Linear Response History Analysis (NLRHA) approach, this research aimed to employ the F2MPA (Flexibly-supported 2 DOF Modal Pushover Analysis) approach in developing fragility curves of flexibly-supported plan-asymmetric structures. To do this task, the F2MPA approach is employed to approximately calculate the seismic non-linear response of soil-RC plan asymmetric building systems considering the eccentricity and soil structure interaction (SSI) simultaneously with lower computational costs. Using an appropriate hysteretic model, the F2MPA-based IDA (Incremental Dynamic Analysis) procedure, developed in this study, can accurately estimate the seismic response of the superstructure considering stiffness deterioration, strength loss and pinching behavior of RC members. To examine the applicability of the proposed method, an 8-story RC dual lateral load resistant building under an ensemble of near fault pulse-like events is used. The comparison of the NLRHA-based and F2MPA-based fragility functions showed a good agreement. Considering the time effectiveness of the proposed approximate method (less than the 0.01 of the NLRHA method), the method is found to be very attractive for practical soil-asymmetric structures. Negligence of the SSI effect for a given structure could be taken into consideration if this approximate fragility analysis does not highlight major SSI effects.
