Multi-variate seismic fragility assessment of CLT coupled wall systems

The cross-laminated timber coupled wall (CLT-CW) system, a recently proposed timber-based structural system, has limited understanding of its seismic performance. The existing research in probabilistic seismic fragility assessment (PSFA) of CLT buildings reveals gap, particularly regarding comprehensive evaluation of CLT-CW systems and the impact of its various design parameters. To fully describe the state of the post-earthquake performance of structures, state-of-the-art studies recommend using multi-variate fragility analysis. Accordingly, this article presents a bi-variate PSFA of CLT-CW systems using two engineering demand parameters: the maximum and residual inter-story drift ratios. For the seismicity of Vancouver, British Columbia, Canada, 11 prototype buildings are evaluated considering different design parameters: coupling ratio, coupling beam shear force profile, CLT wall configuration, building story height, and ductility-related seismic force modification factor. Bi-dimensional numerical models of the systems are developed in OpenSees, and incremental dynamic analyses are performed using 30 ground motion records. Three limit state capacities and three limit state function combinations are utilized to develop probabilistic seismic fragility curves. The fragility curves under the different limit state function combinations are compared, and the effect of the different design parameters is investigated. This study contributes to a deeper understanding of the seismic performance of CLT-CW systems, assisting engineers and researchers in assessing seismic risk and developing seismic-resilient structures.