ERI: Experimental Framework for Post-Fire Seismic Rehabilitation of Mass Timber Connections under Sequential Fire-Earthquake Loading

Wildfire and seismic hazards increasingly co-occur in regions with growing mass timber construction. While mass timber offers exceptional sustainability, strong seismic resistance, and predictable fire performance, critical questions remain regarding how fire-damaged buildings can be rehabilitated to safely withstand future earthquakes. This Engineering Research Initiation (ERI) award establishes an experimental framework to evaluate the post-fire seismic performance and repairability of mass timber structural connections subjected to sequential fire and earthquake hazards. Structural connections govern both lateral resistance and post-disaster repairability, making their residual performance central to rehabilitation decisions. However, engineers currently lack validated testing protocols, repairability benchmarks, and evidence-based criteria needed to guide repair-versus-demolition decisions. To bridge this gap, the project will develop practical methods to evaluate fire-damaged connections, restore their seismic performance, and quantify repair effectiveness. The outcomes will reduce unnecessary building demolition, lower post-disaster recovery costs, and improve the resilience of timber infrastructure exposed to compounding hazards. Additionally, the project will provide hands-on research and technical training opportunities for undergraduate and graduate students, equipping the next generation of engineers to advance multi-hazard resilience. Fire exposure degrades mass timber connections through bolt preload loss, wood embedment failure, and localized fiber degradation, severely compromising their ability to resist subsequent seismic loading. To address these distinct damage mechanisms, this project will develop an experimental rehabilitation framework that integrates three targeted strategies based on heat-activated alloys, sacrificial plug inserts, and hybrid shear keys. The research objectives are to: (1) quantify fire-induced changes in connection load-deformation response, stiffness, ductility, and failure modes; (2) develop and refine rehabilitation techniques that restore bolt preload, wood embedment capacity, and shear transfer; and (3) evaluate the seismic performance of rehabilitated connections through component-scale cyclic testing followed by system-level shake-table validation. Using this framework, the project will establish practical repairability metrics, preliminary fragility curves, and post-fire performance-based criteria to support evidence-based rehabilitation guidance and future mass timber design standards. Project findings, datasets, and experimental protocols will be disseminated through NSF's DesignSafe repository and shared with practicing engineers, industry stakeholders, and code-development organizations to inform engineering practice and future design provisions. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.