Development of Fragility Curves and Assessment of Mass Irregular Structures with Fixed Base and Base Isolated Under Multiple Earthquakes

Structures are usually built to withstand the mainshock, aftershocks offer extra difficulties. Aftershocks frequently occur following an earthquake result in multiple earthquakes, therefore they are not isolated events. Due to damage advancement, and stiffness and strength deterioration, a damaged structure might collapse under a multiple earthquakes. Based to a probabilistic perspective, the current study investigates the effect of multiple earthquakes on the likelihood of buildings to collapse. This study's primary objective is to determine how multiple earthquakes affect fixed- and base-isolated structures. In this context, recorded 14 single and 7 multiple earthquakes with various properties were used to examine and assess three-dimensional reinforced concreteframes with four-storey, having fixed base and isolated base. Dynamic analysis, of the three-dimensional structures are carried out in SAP2000. Fragility curves for fixed base and base isolated structures were produced using the incremental dynamic analysis approach. To find the effect of mass irregularity due to single and multiple earthquakes, mass irregularity is placed at every floor level in each structure. The results are compared in terms of floor displacements, floor accelerations, storey drift, base shear, residual displacement, and probability of collapse for fixed base and base isolated structures. The findings highlight the importance of analyzing the structures subjected to multiple earthquakes. The probability of collapse is reduced for mass irregular structures with base isolation in comparison with fixed base structures, when subjected to multiple earthquakes. The designer's should select base isolation over the fixed base system when the building's location may suffer multiple earthquakes more frequently.