Probabilistic Performance Assessment of Base-Isolated Hospital Building Under Earthquake Excitations

Fragility functions provide important tools to the designer for reliable dynamic performance assessment of structures, considering the effects of uncertainty in the earthquake excitations. Given the catastrophic impact of the recent earthquakes on society, it is of prime importance to maintain operational condition in hospitals during earthquakes, for effective disaster management. Therefore, the present study demonstrates the advantages of base isolation of lifeline structures, such as hospitals, in ensuring continued functionality of the structure during and after earthquakes. An existing irregular-shaped hospital building in Avezzano (L’Aquila, Italy) is considered for evaluation of its seismic performance. The efficacy of three different base isolation systems (BISs), namely, high damping rubber bearings (HDRBs), lead rubber bearings (LRBs), and friction pendulum systems (FPSs), are investigated in the vibration control of the considered hospital building, when subjected to site-specific bidirectional earthquake excitations. Nonlinear dynamic analyses are conducted on the 3-dimensional model of the base-isolated hospital buildings to evaluate its seismic response. Further, fragility curves of the various uncontrolled and base-isolated structures are developed based on the limit state of maximum acceleration response corresponding to (a) tolerance level of the building occupants and (b) slight damage of the nonstructural equipment. Results show that the performance of the HDRB-isolated structure is supreme, followed by the LRB-isolated structures, and subsequently the FPS-isolated structures, under the given scenario. Nevertheless, all the BISs could effectively reduce the structural responses of the irregular-shaped hospital building under the bidirectional earthquake excitations.