Shear Design and Evaluation of Concrete Structures

这项长期研究计划的目标是了解开裂的钢筋混凝土如何传递剪切，并利用这种理解为新钢筋混凝土结构的剪切设计和现有结构的评估开发简单，通用，合理和准确的程序。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。在过去五年中，在提高剪切设计条款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缺陷。这种结构在地震中特别容易倒塌。今后五年的主要目标是发展各种工具，以决定必须修复哪些结构，并提供这样做的实际程序。这将通过对钢筋混凝土的密集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载荷。最近开发的技术将得到改进，使临界裂纹的形成、打开、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特征裂纹模式。将研究荷载循环对含有具有代表性的现有结构中钢筋细节的构件的裂纹扩展和粘结劣化的影响，并模拟实际结构中发生的收缩约束和热运动的影响。实验研究将辅以广泛的非线性三维有限元分析。最后，我们将开发出简单的分析模型，供实践工程师用于评估现有结构的抗剪安全性。该研究将由研究生进行，他们将深入了解极端载荷下钢筋混凝土结构的剪切行为。经过这样的研究，他们将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.