Optimization-based seismic design for tall timber buildings with hybrid cross-laminated timber walls coupled with steel link beams and hold-down dampers

Abstract

Coupled walls (CWs) composed of cross-laminated timber (CLT) walls and steel link beams (SLBs) represent a high-performance option for lateral force-resisting systems in tall timber buildings. This paper proposes a computationally feasible optimization-based seismic design framework for tall timber buildings equipped with CLT walls coupled with SLBs, and hold-down dampers (HDDs) developing flag-shaped hysteresis behavior. The seismic design was formulated as a combinatorial multiobjective optimization problem in which the cross-section sizes of the SLBs and the capacity of the HDDs were set as design variables. A simulated annealing algorithm was employed to minimize the multiple objective functions, including the maximum section force in the CLT panel and the maximum SLB’s cross-section size and HDD’s uplift capacity. 18-story, 15-story, and 12-story tower-type buildings modeled as two-dimensional finite-element systems were optimized through nonlinear time-history analysis. Seismic performance was evaluated based on the fragility function generated by incremental dynamic analysis. The selected optimal solution showed a non-uniform SLB distribution reduced CLT’s section demand while maintaining the inter-story drift limits. Although the numerical model ignored the flexibility of diaphragms and the torsional modes of the system’s response, this research has displayed an implementation procedure for a heuristic-based performance-based seismic design approach for tall timber buildings with CLT-CW systems.