Seismic Performance and Damage Risk of Modular CLT Housing Using Nonlinear Time History Analysis

The United States (U.S.) faces significant housing challenges, including a shortage of affordable housing and high rates of homelessness. This, combined with the pursuit of sustainable and resilient communities, has positioned Cross-Laminated Timber (CLT) modular structures as a promising alternative due to their environmental, mechanical, and prefabrication advantages. However, a comprehensive study of their seismic performance and risk across the U.S. is needed to establish CLT modular construction as a resilient housing option. Therefore, this thesis assesses the seismic risk and performance of five modular CLT houses, studying (i) the variability of their collapse fragility curves across the U.S., (ii) the conditional probability of collapse under Maximum Considered Earthquake (MCE) intensities, and (iii) the unconditional probabilities of experiencing non-structural damage and collapse within 50 years for ten representative locations. The houses use the latest platform-constructed CLT shear wall lateral-force resisting system included in ASCE 7-22 (2022) and were designed using prescriptive code-based methods to represent a feasible construction alternative. The analyses were conducted under the performance-based earthquake engineering framework. Ground motion data sets were established for three seismic regions: (1) Western U.S. with forward-directivity pulses, (2) Western U.S. without forward-directivity pulses, and (3) Central and Eastern U.S. Numerical models for each house were developed and calibrated using OpenSees to perform nonlinear static and time history analyses. The Multiple Stripe Analysis procedure was used to derive the conditional probability of collapse fragility curves and interstory drift distributions, which, along with generic damage fragilities and seismic hazard curves, estimated the probabilities of non-structural damage and collapse within 50 years at representative locations. The results indicate that differences in ground motion characteristics, including pulse-like motions, do not significantly impact the collapse fragility curves. All houses satisfy the ASCE 7-22 (2022) target of a 10% conditional probability of collapse at MCE intensity. Expected non-structural damage is within acceptable limits compared to common performance objectives. Increasing house strength does not significantly enhance performance in non-structural damage states, as performance is primarily influenced by the hazard curve of the location. The unconditional probability of collapse within 50 years remains conservatively low, satisfying the ASCE 7-22 (2022) performance objective of a 1% probability of collapse within 50 years. In summary, the consistent behavior, low collapse risk, acceptable non-structural damage levels, and potential improvements through performance-based design make modular CLT houses a reliable, resilient, and high-performance seismic housing alternative in the U.S.