Risk-Informed Design Optimization of Vertically Distributed Tuned Liquid Wall Dampers for Multihazard Mitigation

Supplemental damping devices, including passive, semiactive, and active systems, can be employed to reduce vibrations caused by various hazards. This paper examined tuned liquid column dampers (TLCDs), a specialized type of tuned mass damper typically used to reduce the response of the structure around a specific frequency. A variation of the tuned liquid damper previously studied by the authors is a tuned liquid wall damper (TLWD), in which multiple liquid columns are embedded within a RC shear wall. The TLWD eliminates the space requirement of a conventional tuned liquid damper by distributing the liquid mass vertically into multiple columns throughout the structural shear wall system, and enables reaching a higher frequency range through the design of the TLWD geometries. This study investigated the optimal design of TLWD systems to mitigate multiple hazards, in particular nonsimultaneous wind and seismic hazards, based on a life-cycle cost (LCC) objective function. This was done using a probabilistic life-cycle analysis procedure that leveraged Bayesian optimization (BO) to search for the most promising permutation of tuning parameters that minimize the LCC under the design loads, with Monte Carlo simulations used to propagate the record-to-record variability of wind and seismic hazards. The proposed procedure was demonstrated on a 20- and a 42-story building subjected to nonsimultaneous wind and seismic excitations. The vertically distributed TLWDs were subjected to geometric constraints provided by the wall systems, and tuned to multiple frequencies enabling multimode mitigation. Afterward, the optimal tuning parameters were identified using the LCC-BO algorithm. Results showed that the multimode TLWD tuned with optimal tuning parameters effectively mitigated both wind and seismic hazards, leading to 32.8% and 43% total LCC reduction for the 20- and 42-story buildings, respectively, compared with the buildings without dampers, excluding the cost of the mitigation system. A performance comparison with a traditional tuned liquid column damper (TLCD) installed at the top of the buildings demonstrated that the multimode TLWD system outperformed the TLCD with an approximate 9% reduction in LCC for both the 20- and 42-story buildings. (C) 2021 American Society of Civil Engineers.