Performance-based design of multi-story timber-steel hybrid structures under extreme hazards

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Timber-steel hybrid structures are a novel solution towards sustainable multi-story construction. The combination of steel framing with engineered wood slabs and wall panels leads to overall building weight reduction, while allowing for a decrease in construction-related emissions. This innovative structural system presents cutting-edge feats of engineering, but is also susceptible to increasing threats from natural and man-made hazards. Lack of comprehensive knowledge regarding structural performance of this new system against extreme events poses a danger to life safety and substantial economic loss. Despite research interest, reticence prevalent in the industry due to these knowledge gaps has impeded the adoption of hybrid timber structural systems in North America. Recent studies have investigated seismic response of timber-steel hybrid structures. However, no systematic framework is available for reliable industrial applications. Additionally, not much information is available regarding global structural behavior under fire. In-depth research is needed, particularly for investigating structural behavior under cascading multi-hazard scenarios, such as fire following an earthquake. For structures where code-based guidelines are still nascent, performance-based design methodologies are an attractive alternative. This requires the evaluation of structural response under realistic hazards, coupled with a thorough quantification of risks for overall structural performance. The proposed research program will seek to establish a robust performance-based design and assessment framework for multi-story timber-steel hybrid structures under earthquake, fire, and multi-hazard scenarios. Typically, seismic risk for wooden structures has been quantified as: risk = hazard x exposure x vulnerability. Systematic risk assessment incorporates uncertainties associated with each of the components of this model. This research program will follow a similar approach to characterize realistic earthquake, fire and cascading hazards for hybrid timber-steel structures. Site- and occupancy- specific hazard intensity measures will be characterized. Detailed analytical and experimental analyses will be conducted to calibrate structural behavior under the characterized hazards. Damage assessment metrics will be established for each loading scenario. Additionally, this research will characterize system-level resilience in the shape of response and recovery times and repair costs for such construction. Training of highly qualified personnel will be a prime focus of the research program. Benefits to the research community and Canada will be two-fold: first, better understanding of overall performance of hybrid timber-steel structures will help improve design practice ensuring better life safety; and secondly, the new knowledge will advance Canada's standing in terms of hybrid wood construction, leading to potential growth of the forestry sector and ensuing economic benefits.