Risk-based optimization of seismic mitigation devices constrained by user-defined components importance

Abstract

The system optimization of complex structures is to achieve the overall best behaviour, however, specifications and engineers often pay more attention to the seismic performance of critical components. To comprehensively consider the requirement from theoretical research and practical engineering, a constrained optimization method of seismic mitigation devices for complex structures is proposed in this study, considering the user-defined importance of critical components. The seismic damage probability of individual components is defined as constrained functions (CFs). The overall probabilistic seismic performance of the bridge system is formulated as the objective function (OF) to carry out optimization analysis within the admissible region obtained by CFs. The surrogate functions between the variables and OF/CFs are formulated by the proposed Hazard-related Response Surface Method (H-RSM). A three-dimensional long cable-stayed bridge with a mitigation device of the fluid viscous damper (FVD) is constructed as the case-study model via FEM. Three constrained conditions are imposed by restricting the CFs less than a user-defined threshold to satisfy different safety requirements of the pylon, bearing and FVD. Different protection levels of the pylon are investigated to compare the constrained and unconstrained optimization methods. The influence of the maximum displacement of FVD on the optimal variables is also investigated.