Seismic design and performance evaluation of post-tensioned CLT shear walls with coupling U-shaped flexural plates in Canada

Abstract

Post-tensioned cross-laminated timber (PT-CLT) walls coupled with U-shaped flexural plates (UFPs) have proved to be a low-damage seismic force-resisting system (SFRS) due to their self-centering capability and stable energy dissipation. Global efforts have been made to explore the applicability of PT-CLT walls as primary SFRSs in mass timber buildings. Adoption of the sixth-generation Seismic Hazard Model (SHM6) in the 2020 National Building Code of Canada resulted in a nationwide increase in seismic hazard. Given the increased popularity of mass timber buildings and the elevated seismic hazard, a comprehensive study is required to examine their performance in high seismic regions with complex seismotectonics, such as southwestern British Columbia, Canada. Therefore, this article presents the seismic design and performance evaluation of three-, six-, and nine-story mass timber buildings that use PT-CLT shear walls with coupling UFPs as SFRS for the seismicity of Vancouver, Canada. The prototype buildings were designed using the direct displacement-based design (DDBD) approach considering the SHM6. Two-dimensional fiber-based numerical models were developed in OpenSeesPy and validated with full-scale quasi-static cyclic and shaking table experimental tests. Nonlinear static and response history analyses were carried out to assess the structural responses and validate the DDBD procedure. Incremental dynamic analyses (IDA) were conducted using 80 ground motions selected for each building to develop fragilities and to estimate collapse margin ratios (CMRs). The IDA results demonstrate that all the examined buildings have adequate CMRs compared with acceptable limits in the literature. Overall, this study demonstrated that PT-CLT walls with coupling UFPs are a potential SFRS alternative in Canada’s high seismic-risk regions.