Robust Stochastic Design of Base-isolated Structural Systems

The development of a general framework for robust reliability-based design of base-isolated structural systems under uncertain conditions is presented. The uncertainties about the structural parameters as well as the variability of future excitations are characterized in a probabilistic manner. Isolation elements composed of nonlinear lead rubber bearings are used to model the isolation system. The optimal design problem is formulated as a nonlinear constrained minimization problem involving multiple design requirements, including reliability constraints related to the structural performance. Failure events defined by a large number of random variables are used to characterize the reliability of the system. A sequential optimization approach based on global conservative, convex, and separable approximations is implemented for solving the optimization problem. An example problem that considers a 10-story building under stochastic ground excitation illustrates the beneficial effects of base-isolation systems in reducing the superstructure response.