Risk‐based optimization of concentrically braced tall timber buildings: Derivative free optimization algorithm

Mass timber materials are attractive alternatives for tall-timber buildings (TBs), where the need for sustainability is apparent. Innovative structural systems and design methodologies are needed to fulfil performance requirements according to modern performance based approaches. This paper deals with the design and optimization of buckling restrained braces as earthquake protection system for tall-TBs through risk-based design procedure. This procedure controls the mean annual frequency of exceedance of several limit states evaluated through a SAC-FEMA approach and using response spectrum linear analyses on linearized models for demand assessment. The features of the optimization procedure and the linearized models are shown through an application on a 20-story mass-TB located in a high seismic zone. The optimization is executed through a derivative-free algorithm, the generalized pattern Search, adopting several solution strategies whose efficiency and effectiveness for this kind of applications are shown and discussed. Finally, the results are compared and validated through the execution of non-linear analyses within a multiple stripe framework.