Shear Design and Evaluation of Concrete Structures

这一长期研究计划的目标是了解开裂的钢筋混凝土是如何传递剪力的，并利用这一理解为新的钢筋混凝土结构的抗剪设计和现有结构的评估制定简单、通用、合理和准确的程序。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。在过去五年中，在提高剪切设计规定的质量方面取得了重大进展，这将大大减少新混凝土结构发生灾难性剪切破坏的机会。然而，我们现在也知道，许多现有的混凝土结构在抗剪能力方面存在不足。这类建筑在地震中特别容易倒塌。今后五年的主要目标是开发工具，以决定必须修复哪些结构，并提供这样做的实际程序。这将通过对受荷载作用的钢筋混凝土密集仪器化构件进行试验，模拟实际遇到的实际情况。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、张开、扩展和滑动，从而准确地定义即将到来的剪切坍塌的特征裂纹模式。研究循环荷载对构件裂缝扩展和粘结劣化的影响，模拟实际结构中发生的收缩和温度运动的约束效应。实验研究将辅之以广泛的非线性三维有限元分析。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，他们将有能力为加拿大关键基础设施的安全评估做出贡献。

The objectives of this long term research program are to understand how cracked reinforced concrete transmits shear and to use this understanding to develop simple, general, rational and accurate procedures for the shear design of new reinforced concrete structures and for the evaluation of existing structures. Shear failures can cause concrete structures to collapse without warning and hence, are of critical concern for public safety. In the last five years, major progress has been made in improving the quality of shear design provisions which will greatly reduce the chance of catastrophic shear failures for new concrete structures. However, we also now know that many existing concrete structures are deficient in shear capacity. Such structures are particular prone to collapse during earthquakes. The major objective of the next five years is to develop the tools to decide which structures must be repaired and to provide practical procedures to do so. This will be done by conducting experiments on intensively instrumented elements of reinforced concrete subjected to loadings which simulate the actual conditions encountered in practice. Recently developed techniques will be improved to enable the formation, opening, propagation and sliding of critical cracks to be recorded so that the characteristic crack patterns of impending shear collapse can be accurately defined. The influence of cycles of load on crack propagation and bond deterioration for members containing reinforcement details representative of those in existing structures will be studied and the effects of restraint of shrinkage and thermal movements, which occur in actual structures, will be simulated. The experimental studies will be supplemented with extensive non-linear 3D finite element analyses. 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 loadings. After such research they will be equipped to contribute to the safety assessment of Canada's critical infrastructure.