Innovative detailing for shear in concrete using high performance materials

现有的钢筋混凝土剪切设计模型采用基于应力的组合方法来计算构件的强度，既有混凝土的贡献，也有基于桁架类比的剪切钢筋的贡献。这些模型限制了设计中允许的剪切钢筋的最大强度，以限制破坏时的裂缝宽度。剪切钢筋的最大间距由基于内部桁架的假设角度的经验规则定义。自1960年代以来的有限研究表明，当放松这两个标准中的任何一个时，安全设计都是可能的。改进的剪切能力模型直接考虑了剪切钢筋应变和间距，将允许经济和安全地使用现代、耐用的加固材料作为箍筋。他们说，这项研究将通过实验室和数值研究来调查抗剪钢筋纵向间距对抗剪能力的影响。将考虑代表新建筑的抗剪钢筋布置，以及适用于修复应用的剪力桩结构。还将考虑由于使用高强度钢或纤维增强聚合物材料而导致的破坏时更高的箍筋应变的影响。在实验研究中，将特别强调现有试验数据很少的配置，包括具有宽配筋间距的大构件。更多的非线性数值模型、新的试验数据和对现有设计方法的严格检查将允许开发一种新的基于应变的剪切设计方法，该方法可以考虑箍筋间距，并结合箍筋的力学性能。该模型将允许在实践中发生更多的创新细节，对于采用稀疏间距的高性能加固材料的构件。此外，预测现有构件的能力将被提高，从而将不必要的和昂贵的修复减少到最小。

Existing shear design models for reinforced concrete use a stress-based compositional approach to member strength, from both a concrete contribution and from a shear reinforcement contribution based on a truss analogy.  These models limit the maximum strength of the shear reinforcement permitted in design, in order to limit crack widths at failure.  Maximum spacing of the shear reinforcement is defined by empirical rules based on an assumed angle for the internal truss.  Limited studies since the 1960's have shown that safe designs are possible when either of these criteria are relaxed.  Improved capacity models for shear that directly consider both the shear reinforcement strains and spacing, will permit economical and safe use of modern, durable reinforcement materials as stirrups.     This study will investigate influences on shear capacity from the longitudinal spacing of shear reinforcement, through laboratory and numerical studies.  Shear reinforcement arrangements representative of new construction will be considered, along with shear dowel configurations suitable for rehabilitation applications.  The influence of higher stirrup strains at failure, resulting from the use of high strength steel or fibre reinforced polymer materials, will also be considered.  A special emphasis in experimental investigations will be placed on configurations where little existing test data is available, including large members with wide reinforcement spacing.     Non-linear numerical models, the new test data, and a critical examination of existing design methods will permit development of a new strain-based shear design approach which can account for stirrup spacing, in combination with the stirrup mechanical properties.  This model will permit more innovative detailing to occur in practice, for members with sparsely spaced high performance reinforcing materials.  Furthermore, the ability to predict the capacity of existing members will be improved, thereby minimizing unnecessary and costly rehabilitation.