Seismic performance of steel concrete composite structures

In this paper the seismic performance of a sample composite steel concrete frame has been investigated. The study initially focuses on the calibration of a simple numerical model, by comparing its predictions to the actual experimental response from a test program carried out at the ELSA in Ispra. A set of twenty ground motions having mean spectrum compatible with the design one for increasing values of PGA has been assumed to represent the seismic excitation and nonlinear dynamic analysis has been performed to find the response. For each level of seismic input, seismic response domain of the sample structure has been described by assuming a Gaussian model. Four fragility curves have been obtained representing the probability of exceeding the assumed limit states, expressed in terms of interstorey drift. It has been found that the considered limit conditions related to occurrence of damage are rather realistic, even if they are not specific for composite structures. On the contrary, the assumed limit values for ultimate conditions need to be better calibrated for composite structures.