Performance-based wind design of tall mass timber buildings with coupled post-tensioned cross-laminated timber shear walls

Engineered timber panels, such as cross-laminated timber (CLT), have enabled tall mass timber buildings to reach heights equivalent to mid-rise concrete and steel buildings. Tall mass timber buildings are lighter and more flexible than their concrete and steel equivalents, which makes their design wind-critical. The current prescriptive code-based design of main wind force resisting systems (MWFRSs) only considers buildings’ linear-elastic capacity, resulting in costly designs requiring commercially unavailable timber cross sections. This prevents engineers from fully utilizing timber as MWFRS and limits the height that mass timber buildings can reach. In performance-based wind design (PBWD), nonlinear-inelastic deformation in specially designed and detailed parts of MWFRSs enables an optimal design. However, controlling damage accumulation in structures can be challenging due to the substantial mean component of wind loads in the along-wind direction. To this end, self-centering systems such as coupled post-tensioned CLT (PT-CLT) walls can offer a solution. However, despite extensive analytical and experimental studies on the use of PT-CLT walls as seismic force-resisting systems, their use as MWFRSs has not been explored. Therefore, this paper proposes the use of PT-CLT walls as MWFRSs in tall mass timber buildings and develops a new PBWD approach for their design. To demonstrate the applicability of the PBWD approach, 8- and 16-story prototype mass timber buildings hypothetically located in Toronto, Canada, were designed using PBWD and load information from wind tunnel tests. For performance assessment, three-dimensional multi-spring numerical models were developed in OpenSeesPy and validated with full-scale quasi-static cyclic and shaking table experimental tests. Performance assessments using nonlinear response history analysis (NLRHA) under simultaneous along-, across-, and torsional-wind loads for 36 wind directions were carried out. The results indicate that the proposed PBWD framework is practical and effective for designing PT-CLT shear walls as MWFRSs in tall mass timber buildings.