High strain rate characteristics of wood arising from blast and impact loading

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The improved dimensional stability and fire performance as well as broader availability of engineered wood products, such as glued-laminated timber (glulam) and cross-laminated timber (CLT), have contributed to a renewed interest in extending the concept of wood-based systems from the typical low-rise residential construction to mid- and high-rise applications. High-profile structures (e.g. embassies, military, office high-rise, gathering venue) often face a risk of a deliberate attack and thus are analyzed for blast loads. Despite its inclusion in the Canadian blast design standard, there is limited guidance provided for the analysis and design of wood structures to blast loading. The emergence of tall timber and timber-hybrid structures could increase the likelihood of a high-profile structure to be built using wood. As such, recent efforts from both the industry and research community have been directed towards establishing the blast response of wood structures. The current knowledge of the wood material properties and failure modes is limited to the lower strain rate range experienced during blast and impact loading. Since the dynamic increase factor is directly a function of the strain rate, there is a fundamental need in research to establish the properties and response at higher strain rates. The objective of this research program is to characterize and improve the response of timber structures at a system level under high strain rates (HSR) arising from blast and impact loading. This long-term goal will be achieved by initially establishing the isolated behaviour of timber elements through experimental studies and development of analytical models. Impact tests characterizing the wood material properties at a component and system level under HSR will be conducted. The HSR behaviour of finger joints will also be investigated in isolation as well as part of full-scale elements to determine its effect on the global response. Novel retrofitting and strengthening strategies using fibre reinforced polymers (FRP) will also be investigated in order to provide ductility, which is inherently lacking in wood members, as well as to develop finite element models. Graduate students under this program will acquire a broad understanding of structural dynamics, design of timber structures, and a unique expertise related to their project, thus making them widely marketable in the research and development sector, engineering and consulting, and academia. Understanding the performance of wood structures under impact and blast loading will result in new knowledge at HSR about: the material properties (dynamic increase factor), response limits, strengthening and retrofitting strategies using FRP, and numerical and finite element models to accurately predict the response. The outcomes from the proposed research program will directly influence current design guidelines in the Canadian blast design standard and assist engineering in their analysis and design.