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分析工具，结构工程师可以用来设计新的结构和评估现有混凝土结构的安全性。剪切破坏可以导致混凝土结构在没有警告的情况下倒塌，因此，对公共安全至关重要。现在已经知道，用于现有混凝土基础设施的相当大一部分的较旧的北美剪切和扭转设计程序可能导致建筑物、桥梁、筒仓和核电厂可能没有足够的安全裕度来防止这种故障。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强烈仪器元件进行实验来完成，这些元件承受模拟实践中遇到的实际条件的负载。最近开发的技术将得到改进，使形成，传播和滑动的临界裂纹被记录，使即将剪切崩溃的裂纹图案的特性可以准确地定义。将研究反向循环荷载对含有代表旧结构中钢筋详图的构件的裂纹扩展和粘结劣化的影响，并模拟收缩和热运动约束的影响。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，适用于实践工程师使用，以评估现有结构的剪切安全将开发。这项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。在进行这种研究之后，他们将有能力为加拿大重要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.