Numerical modeling and seismic performance of post-tensioned cross-laminated timber rocking wall systems

Alex William Wilson

An interest in tall, mass timber buildings in the U.S. have resulted in the introduction of post-tensioned (PT) cross-laminated timber (CLT) rocking walls, a resilient lateral system with self-centering capabilities that provides a possible solution for low- to mid-rise mass timber buildings. This system includes hysteretic damping devices that couple individual wall panels, increasing stiffness, resistance, and energy dissipation. Modeling methods for PT CLT rocking walls are limited with regards to software implementation, resiliency assessment capabilities, and computational efficiency. In addition, overall assessment of full-scale building response has been limited with no assessment regarding economic performance, which leaves a high degree of financial uncertainty for initial developers and insurance agencies. Two new modeling methods for PT CLT rocking walls that may be implemented into common commercial software were developed and validated against experimental tests. A high-order model, capable of investigating stress distributions, crushing deformation, and global moment-rotation behavior in the wall panel was developed. A computationally efficient reduced-order model that captures the global moment-rotation behavior of a given wall configuration was developed for use in nonlinear time-history analysis of large buildings. Using these techniques, both a low- and mid-rise archetype model with PT CLT rocking walls were characterized. Both archetypes underwent suites of time-history analysis at design and maximum considered earthquake level events, utilizing far-field and near-fault ground motions, where global, deformation-controlled, and force-controlled responses were assessed. These models were also utilized to execute a performance assessment to investigate the economic risk associated with the nonstructural component make-up using several metrics useful to investors. Both the high- and reduced-order model compared well against experimental tests for both single and coupled PT CLT rocking walls. Both archetypes were able to meet predetermined performance objectives and code acceptance criteria, while the assessed responses of the low- and mid-rise archetype proved to be more sensitive to ground motion pulses and far-field motions, respectively. For all assessed intensity levels, both buildings showed that nonstructural repair could be performed at a cost cheaper than total replacement. The low- and mid-rise building exhibited better nonstructural economic performance in high and low intensity level events, respectively

Numerical modeling and seismic performance of post-tensioned cross-laminated timber rocking wall systems

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