Multiobjective Design of Supplemental Seismic Protective Devices Utilizing Lifecycle Performance Criteria

Abstract

The cost-effective design of seismic protective devices considering multiple criteria related to their lifecycle performance is examined, focusing on applications to fluid viscous dampers. The adopted framework is based on nonlinear time-history analysis for describing structural behavior, an assembly-based vulnerability approach for quantifying earthquake losses, and on characterization of the earthquake hazard through stochastic ground motion modeling. The probabilistic (lifecycle) performance is quantified through the expected value of some properly defined risk consequences measured over the space of the uncertain parameters (i.e., random variables) for the structural system and seismic hazard. The main design objective considered is the mean total lifecycle cost, composed of the upfront protective device cost and the present value of future earthquake losses. For incorporating risk-aversion attitudes in the decision-making process, an additional objective is examined, corresponding to consequences (repair cost in the example considered in this study) with a specific small-exceedance probability over the lifetime of the structure. This explicitly accounts for low-likelihood but large-consequence seismic events and ultimately leads to a multicriteria design problem. To support the use of complex numerical and probability models, a computational framework relying on kriging surrogate modeling is adopted for performing the resultant multiobjective optimization. The surrogate model is formulated in the so-called augmented input space, composed of both the uncertain model parameters and the design variables (controllable device parameters), and therefore is used to simultaneously support both the uncertainty propagation (calculation of risk integrals for the lifecycle performance) and the design optimization. As an illustrative example, the retrofitting of a three-story building with nonlinear fluid viscous dampers is examined.