Shear and Torsion Response of Reinforced Concrete Structures

这一长期研究计划的目标是提高对裂纹钢筋混凝土传递剪应力的机制的理解，并利用这种理解开发分析工具，结构工程师可以使用这些工具来设计新结构和评估现有混凝土结构的安全性。剪切破坏可能会导致混凝土结构在没有预警的情况下倒塌，因此，对公共安全来说是至关重要的。现在已经知道，北美较老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会导致建筑物、桥梁、筒仓和核电站可能没有足够的安全裕度来抵御此类故障。这类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组合扭转和剪切的理解，并开发工具来决定哪些结构必须修复。这将通过对承受载荷的钢筋混凝土构件进行实验，模拟实际遇到的实际情况来完成。最近开发的技术将得到改进，以便能够记录临界裂纹的形成、扩展和滑动，以便准确地确定即将到来的剪切坍塌的裂纹模式的特征。研究反复荷载对钢筋混凝土构件裂缝扩展和粘结劣化的影响，模拟收缩和温度运动的约束效应。实验研究将辅以广泛的二维和三维非线性有限元分析。最后，将开发适合于实习工程师用于评估现有结构的剪切安全性的简单分析模型。这项研究将由研究生进行，他们将对钢筋混凝土结构在极端荷载下的剪切性能有深入的了解。在这样的研究之后，他们将能够为加拿大关键的混凝土基础设施的安全评估做出贡献。

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.