Shear and Torsion Response of Reinforced Concrete Structures

这项长期研究计划的目标是提高对开裂钢筋混凝土传递剪切应力的机制的理解，并利用这种理解开发结构工程师可以用来设计新结构和评估现有混凝土结构安全性的分析工具。剪切破坏可能导致混凝土结构在没有预警的情况下倒塌，因此对公共安全至关重要。现在已经知道，北美旧的剪切和扭转设计程序用于现有混凝土基础设施的很大一部分，可能导致建筑物，桥梁，筒仓和核电站可能没有足够的安全余地来应对这种故障。这种结构在地震中特别容易倒塌。***未来五年的主要目标之一是提高对扭转和剪切组合的理解，并开发工具来决定哪些结构必须修复。这将通过对钢筋混凝土的高强度仪器元件进行实验来完成，这些元件受到模拟实践中遇到的实际情况的加载。最近开发的技术将得到改进，使临界裂纹的形成、扩展和滑动能够被记录下来，以便能够准确地定义即将发生剪切崩溃的裂纹模式的特征。将研究反向循环加载对含有具有代表性的旧结构中钢筋细节的构件的裂纹扩展和粘结劣化的影响，并模拟收缩约束和热运动的影响。实验研究将辅以广泛的非线性二维和三维有限元分析。最后，简单的分析模型，适合使用的执业工程师评估现有结构的抗剪安全将开发。该研究将由研究生进行，他们将深入了解极端荷载下钢筋混凝土结构的剪切行为。经过这样的研究，他们将有能力对加拿大关键的混凝土基础设施的安全评估作出贡献。

The objectives of this long-term research program are to improve understanding of the mechanisms by which cracked reinforced concrete transmits shear stresses and use this understanding to develop analytical tools which structural engineers can use to design new structures and evaluate the safety of existing concrete structures. Shear failures can cause concrete structures to collapse without warning and, hence, are of critical concern for public safety. It is now known that older North American shear and torsion design procedures used for a significant portion of existing concrete infrastructure can result in buildings, bridges, silos and nuclear power plants which may have inadequate margins of safety against such failures. Such structures are particularly prone to collapse during earthquakes.***One of the major objectives of the next five years is to improve the understanding of combined torsion and shear and develop the tools to decide which structures must be repaired. This will be done by conducting experiments on intensely instrumented elements of reinforced concrete subjected to loading that simulate the actual conditions encountered in practice. Recently developed techniques will be improved to enable the formation, propagation and sliding of critical cracks to be recorded so that the characteristics of crack patterns of impending shear collapse can be accurately defined. The influence of reversed cyclic loading on crack propagation and bond deterioration for members containing reinforcement details representative of those in older existing structures will be studied and the effects of restraint of shrinkage and thermal movement will be simulated. The experimental studies will be supplemented with extensive nonlinear 2D and 3D finite element analysis. Finally, simple analytical models suitable for use by practicing engineers to evaluate existing structures for shear safety will be developed. The research will be conducted by graduate students who will develop a deep understanding of the shear behaviour of reinforced concrete structures under extreme loads. After such research they will be equipped to contribute to the safety assessment of Canada's critical concrete infrastructure.