Strength and Long-term Behaviour of Masonry

该提案分为三个主题。在第一，我建议追求裂纹扩展的基本机制(s)准脆性材料最初被压缩只有一个方向。结果不仅适用于砌体，也适用于混凝土、岩石等。在拉伸中，来自载荷的应力强度与材料的断裂韧性进行比较。当前者到达后者时，发生断裂。对于压缩没有等效的，所以我们预测压缩骨折的能力要比预测拉伸骨折差得多。基本机制尚未阐明，因此我建议研究驱动裂纹扩展的能量来自何处以及缺陷形状和宽度对应力和应变能的影响。与拉伸断裂相比，裂纹宽度和形状是压缩断裂的重要参数。一旦单一裂缝的基本原理从建模和实验工作中变得明显，我建议看看现实中发生的多重裂缝的情况。在第二个主题中，我建议扩展一种建模技术，以观察遗产砌体结构随时间的应力重新分布。由于风化导致的结构外部的恶化已经包括在内，但该模型需要普遍化，以便可以在设计办公室中使用，并在实施干预措施之前评估其效果。这项工作还将有助于更好地了解遗产结构中某些类型裂缝模式的原因。目的是确保为结构提出的干预措施将实际帮助结构并按预期执行。这将有助于为子孙后代保护我们的遗产，正如砖石建筑所表达的那样。在第三个主题中，提出了砌体抗剪强度研究的延续。加拿大砌体结构规范中的砌体抗剪强度方程包括考虑单元截面上的弯矩和剪力。这与极限状态设计理念相反，在极限状态设计理念中，结构元件的强度仅由材料特性估计，并与负载效应的估计进行比较：强度必须大于负载效应。因此，将对文献中的抗剪强度试验和方程进行检查，并进行额外的试验，以确定确定砌体抗剪强度的方法：将对如何调整这部分规范提出建议。对大间距加筋砌体的工作将研究如何通过实验和建模相结合来正确预测其破坏模式和强度。总的来说，拟议的工作范围将带来更好的设计和更安全的结构，特别是砌体和传统砌体，并为使用断裂力学方法预测砌体和混凝土等材料的压缩破坏奠定基础。

The proposal is split into three themes. In the first, I propose to pursue the basic mechanism(s) for crack propagation in quasi-brittle materials initially being compressed in only one direction. Results would not only apply to masonry, but also to concrete, rock etc. In tension, the stress intensity from the loading is compared to the material's fracture toughness. When former reaches the latter, fracture occurs. There is no equivalent for compression, so our ability to predict compressive fracture is much poorer than in tension. The basic mechanisms have not been elucidated, so I am proposing to examine both where the energy comes from to drive crack propagation and the effect of flaw shape and width on stress and strain energy. In contrast to fracture in tension, flaw width and shape appear to be important parameters for compressive fracture. Once the basics for a single crack have become apparent from modelling and experimental work, I propose to look at the case of multiple cracks, as occur in reality. In the second theme, I propose to extend a modelling technique to look at stress redistribution in heritage masonry structures over time. Deterioration of the exterior of the structure due to weathering has been included, but the model needs to be generalized so it can be used in design offices and the effects of interventions assessed before they are implemented. The work will also lead to better understanding of the causes of certain types of crack patterns in heritage structures. The objective is to ensure that interventions proposed for structures will actually help the structure and perform as intended. This will help preserve our heritage, as expressed in masonry buildings, for future generations. In the third theme, continuation of the work on the shear strength of masonry is proposed. The equation for the shear strength of masonry in the Canadian structural masonry code includes the factored moment and shear on the section of the element under consideration. This is contrary to limit states design philosophy in which the strength of a structural element is estimated from material properties alone and is compared to the estimate of the effects of loads: the strength has to be greater than the load effect. Thus, shear strength tests and equations in the literature will be examined and additional tests performed to define a method to determine masonry shear strength: suggestions on how to adjust this part of the code will be made. Work on widely spaced reinforced masonry will investigate how to predict its mode of failure and strength correctly through a combination of experiments and modeling. Overall, the proposed scope of work will result in better designed and safer structures, particularly masonry and heritage masonry, as well as laying the foundation for a fundamental change to predicting compressive failure of materials like masonry and concrete subject to compression - using a fracture mechanics approach.