Investigation of Modular Cross-Laminated Timber Rocking Walls and Rocking Wall -- Light-Frame Shear Wall Dual Systems for Seismic Resilience

Abstract

This dissertation focuses on the development, seismic performance evaluation, and design of post-tensioned cross-laminated timber rocking walls (PT-CLT-RW) for resilient wood construction. This research focuses on experimental, analytical, and numerical investigations into PT-CLT-RW systems, both as stand-alone and as a dual lateral force resisting systems (LFRS) with wood light frame shear walls (LiFS). The first part of this dissertation details the experimental cyclic testing of six large-scale PT-CLT-RW with modular base connections. The tests were designed to replicate the first story of low- to mid-rise mass timber buildings. Two of the walls included a laminated strand lumber (LSL) toe reinforcements aimed at preventing localized crushing damage upon rocking. Several key design parameters were considered, including wall aspect ratio and self-centering ratio to evaluate their effects on the wall's backbone and cyclic behavior. Friction dampers integrated at the base connections provided supplemental damping while maintaining fabrication simplicity. Predictive equations and nonlinear numerical models were developed and validated against test data, offering tools to support seismic design and performance assessment of modular PT-CLT-RW systems with and without toe reinforcement.\ The next part of this dissertation expands on these findings through a parametric investigation into the effects of wall toe reinforcement on seismic performance across a range of building archetypes. These archetypes considered one to four stories and were analyzed with variation in wall aspect ratio, wall thickness, configuration, and toe material. Nonlinear time history analysis was used to investigate the archetype building performance to different earthquake ground motions. Monte Carlo sampling was used to capture material variability, and a mixed-effects logistic regression models was used accounted for record-to-record variability in predicting wall toe damage probability. Results demonstrated that LSL toe reinforcement significantly reduces wall toe damage probability, particularly in low-rise buildings where local crushing may govern design. Fragility curves developed in this study provide generalizable insights for performance-based design of PT-CLT-RW and practical effect of wall of reinforcement on PT-CLT-RWs. Finally, the last part of this dissertation presents an investigation of the seismic performance of a dual LFRS that combines PT-CLT-RWs with conventional wood LiFS. The analysis focused on how the seismic performance was affected by varying the base shear contribution of each subsystem. A practical design methodology for the dual system is presented and applied to a five-story residential archetype located in a high seismic region. NTHA was performed on models representing various base shear allocations between the two subsystems. The findings show that even modest inclusion of PT-CLT-RW (e.g., 15% of base shear) clearly improves seismic performance by reducing collapse probability, inter-story drifts, residual drifts, and soft-story mechanisms, while having minimal impact on horizontal peak floor accelerations. The results support the feasibility of PT-CLT-RW as a complementary system in conventional wood construction to add earthquake resilience. Overall, this research contributes experimental data, validated numerical models, design tools, and performance assessment frameworks to support the adoption of PT-CLT-RW systems in modern seismic design of timber buildings, with the goal of advancing resilient construction practices.