Reliability-based optimization of multiple nonlinear PTMDs for seismic retrofitting of buildings

Abstract

Recent Probabilistic Seismic Hazard Analysis (PSHA) for Chile has indicated a significant increase in PGA values currently adopted in the country. Thus, assessing the reliability of existing buildings and developing tools for seismic retrofitting purposes have become relevant. Adding external passive energy dissipation systems to attenuate seismic oscillations is usually cost-effective. Among the options, pendulum-tuned mass dampers (PTMDs) are attractive due to their performance and simplicity for installation and maintenance issues. Even so, a comprehensive literature survey reveals that reliability-based optimization (RBDO) studies of single and multiple PTMDs cannot be found, to the best of the authors’ knowledge. Hence, this paper aims at performing the RBDO of single and multiple PTMDs of a steel building based on Chilean seismicity. For this purpose, uncertainties in both ground motion and parameters of the mechanical model are considered through seismic vulnerability analysis, which is integrated into an optimization problem. Because strong ground motion must be included, leading the oscillators to sway at large angles, the PTMDs’ non-linear behavior is considered. The results show that for single PTMDs, the classical closed-form expressions can also be successfully employed, but only for higher mass ratios. Furthermore, the optimization for double PTMDs scenario leads to similar performance (as for the single PTMD), but with the associated advantages in installation and maintenance processes, due to their lower masses.