Design optimization of triple friction pendulums for high-rise buildings considering both seismic and wind loads

Triple friction pendulum isolation bearings are typically designed with only earthquakes in mind, or perhaps with a large enough initial friction coefficient to limit displacement under wind loads. However, for potential application in high-rise buildings, wind demand is of greater concern, and the increased flexibility of the structure can lead to wind-induced floor accelerations that exceed the serviceability limit state. To determine the optimum parameters of triple friction pendulum bearings that minimize the structural response under both wind and seismic loading in high-rise buildings, an optimization methodology (fast elitist non-dominated sorting genetic algorithm) is used. Cost functions are proposed that penalize the story drift and floor acceleration under wind and all earthquake hazard level as well as isolation displacement under large earthquake events. First, a genetic algorithm (GA) is adopted to find the optimal parameters of the bearings designed separately for wind and earthquake excitations. However, the triple friction pendulum bearing (TFPB) designed optimally for earthquake excitation provides less than optimal wind-resistant performance and vice-versa. Afterwards, a multi-objective optimization is used which allows for a tradeoff between the seismic isolation and wind-resistant performance. The design parameters of TFPB can then be selected to achieve the best seismic isolation performance while ensuring that the performance under wind-loading meets requirements.