Optimal Design of Three-Dimensional Structures with Hysteretic Braces

Current seismic codes incorporate well-established simplified approaches to protect and mitigate the response of structures under extreme events using hysteretic passive devices. Nevertheless, a systematic and well-establish methodology for the topological distribution and properties of these devices in three-dimensional structures does not exist. In this paper, we develop a computational framework to evolve optimal brace configurations for complicated three-dimensional regular and irregular structures within a given seismic environment consisting of four synthetic ground motions (5% exceedance in 50 years). Non-linear transient dynamic analyses, based upon a Mixed Lagrangian Formulation, are used to evaluate the structures, while the optimization is accomplished with a compact Cellular Automata-based Genetic Algorithm. As a result of the evolutionary process, the optimal placement, strength and size of the dampers are obtained for regular and irregular eight-story steel frame buildings. Interesting brace patterns evolve from the discrete optimization process.