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

改进的尺寸稳定性和防火性能以及更广泛的工程木制品，如胶合层压木材（胶合木）和交叉层压木材（CLT），有助于将木基系统的概念从典型的低层住宅建筑扩展到中高层应用。高层建筑（如大使馆、军事、高层办公楼、聚会场所）通常面临蓄意攻击的风险，因此需要对爆炸载荷进行分析。尽管其已纳入加拿大爆破设计标准，但针对爆炸载荷的木结构分析和设计提供的指导有限。高大的木材和木材混合结构的出现可能会增加使用木材建造高轮廓结构的可能性。因此，工业界和研究界最近的努力都是针对建立木结构的爆炸响应。目前对木材性能和失效模式的了解仅限于爆炸和冲击载荷期间经历的较低应变率范围。由于动态增加因子直接是应变率的函数，因此研究中基本上需要确定较高应变率下的性能和响应。这项研究计划的目的是表征和改善木结构的响应在系统水平下的高应变率（HSR）所产生的爆炸和冲击荷载。这一长期目标将通过实验研究和开发分析模型初步建立木材元素的孤立行为来实现。 将在HSR下进行部件和系统级别的木材特性冲击试验。还将单独研究指形接头的HSR行为，以及足尺元件的一部分，以确定其对整体响应的影响。还将研究使用纤维增强聚合物（FRP）的新型改造和加固策略，以提供木材构件固有的延展性，并开发有限元模型。该计划下的研究生将获得对结构动力学，木结构设计的广泛理解，以及与其项目相关的独特专业知识，从而使其在研发部门，工程和咨询以及学术界广泛销售。了解木结构在冲击和爆炸荷载下的性能将使HSR获得以下新知识：材料特性（动态增加系数），响应极限，使用FRP的加固和改造策略，以及精确预测响应的数值和有限元模型。拟议的研究计划的结果将直接影响加拿大爆破设计标准中的现行设计指南，并协助工程师进行分析和设计。

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.