Seismic behaviour factor calibration for low-damage rocking cross-laminated timber walls

Rocking Cross-Laminated Timber (CLT) wall systems incorporating resilient self-centring hold-down devices have emerged as low-damage alternatives to conventional timber lateral load resisting systems. Although experimental studies have demonstrated stable flag-shaped hysteretic behaviour and minimal residual drift, collapse based calibration of seismic behaviour factors within the New Zealand design framework has not been systematically performed. Recent revisions to the New Zealand National Seismic Hazard Model (NSHM 2022) have led to increased hazard intensities in several regions and underpin the forthcoming loading standard Draft Technical Specifications 1170.5 (DZ TS 1170.5: 2024), necessitating reassessment of collapse reliability for emerging structural systems This study evaluates the collapse performance of balloon-type rocking CLT shear walls using a reliability-based methodology consistent with FEMA P695 (2009) and aligned with the provisions of DZ TS 1170.5:2024 provisions. Nine two-dimensional archetype buildings, including single-wall (2–8 storeys) and coupled-wall (4–12 storeys) configurations, were designed for Wellington Site Class II conditions using displacement-based procedures. Nonlinear models were calibrated against extensive component, sub-assembly, and full-scale experimental testing up to 4.1% drift. Incremental Dynamic Analysis (IDA) was performed using the FEMA P695 far-field ground motion set, and collapse performance was quantified through Collapse Margin Ratios (CMR) and Adjusted Collapse Margin Ratios (ACMR) incorporating spectral shape effects and system uncertainties. All archetypes satisfied both FEMA P695 acceptance criteria and the implied collapse reliability objectives of DZ TS 1170.5. The results demonstrate that rocking CLT walls with resilient hold-downs designed with k μ = 3.5 provide adequate collapse safety margins for single-wall systems up to 8 storeys and coupled-wall systems up to 12 storeys under updated Wellington hazard conditions.