عنوان مقاله [English]
Hybrid concrete-steel buildings in height are usually referred to as buildings that have two lower and upper parts of concrete and steel materials, respectively. Due to the change in mass, stiffness, and damping in the vertical direction, these buildings have complex seismic behavior. Therefore, in this study, the seismic behavior of hybrid concrete-steel buildings at mid-rise height against far-field ground motions was considered. Initially, different models in groups of 7 and 13 stories were designed by considering different ratios of the number of concrete to steel floors. The connection of the upper steel section to the lower concrete section was considered a pin joint in nonlinear modeling in Opensees software due to its implementation. Then incremental dynamic analysis was performed on all models using 22 different far-field records. Also, the maximum structural response diagram at the threshold of complete damage level was obtained according to the outputs of incremental dynamic analysis in different stories under all records along with their average. Fragility curves were extracted at four damage states based on the HAZUS technical report. The results showed that there was a critical area at the junction of the steel frame with the concrete in which the structural response value underwent a sudden change and made this area inclined to much damage, which in the groups of 7 and 13 stories reached 65.2% and 98%, respectively. Finally, the median collapse capacity was obtained from fragility curves for hybrid buildings at different heights. As the number of concrete floors increased, the median collapse capacity of the model increased, which indicated the better seismic performance of the hybrid concrete-steel building. Among the investigated models, the lowest level of fragility was when the ratio of the number of concrete floors to the total floors of the Hybrid concrete-steel building was almost equal to 0.6.