Strength and Long-term Behaviour of Masonry

砌体的强度和长期性能

• 批准号: RGPIN-2018-03772
• 负责人: Shrive, Nigel
• 金额: $ 3.13万
• 依托单位: University of Calgary
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=688710
• 关键词: Strength; Long; term; Behaviour; Masonry

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.

该提案分为三个主题。在第一，我建议追求的基本机制（S）在准脆性材料最初被压缩在一个方向上的裂纹扩展。结果不仅适用于砌体，也适用于混凝土，岩石等在拉伸，应力强度从加载相比，材料的断裂韧性。当前者到达后者时，发生断裂。压缩没有等效值，因此我们预测压缩断裂的能力比拉伸断裂差得多。基本的机制还没有阐明，所以我建议检查能量来自驱动裂纹扩展和裂纹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。一旦一个单一的裂缝的基础已经变得明显的建模和实验工作，我建议看看多个裂缝的情况下，在现实中发生。在第二个主题中，我建议扩展一个建模技术，看看随着时间的推移在遗产砌体结构的应力重新分布。由于风化导致的结构外部劣化已被包括在内，但该模型需要推广，以便在设计办公室中使用，并在实施干预措施之前评估干预措施的影响。这项工作还将导致更好地了解遗产结构中某些类型的裂缝模式的原因。目标是确保为结构提出的干预措施实际上有助于结构并按预期发挥作用。这将有助于为后代保护我们的遗产，如砖石建筑。在第三个主题中，提出了继续关于砌体抗剪强度的工作。加拿大砌体结构规范中砌体抗剪强度的公式包括考虑的构件截面上的系数弯矩和剪力。这与极限状态设计理念相反，在极限状态设计理念中，结构元件的强度仅根据材料特性进行估计，并与载荷效应的估计进行比较：强度必须大于载荷效应。因此，将检查文献中的抗剪强度试验和方程，并进行额外的试验，以确定确定砌体抗剪强度的方法：建议如何调整这部分代码。宽间距配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，拟议的工作范围将导致更好的设计和更安全的结构，特别是砌体和遗产砌体，以及奠定基础的根本变化，预测材料的压缩破坏，如砌体和混凝土受到压缩-使用断裂力学方法。