Systematic study on the shear behavior of reinforced concrete members with regard to the transition of members without and with shear reinforcement

抗剪性能是结构混凝土中一个复杂而重要的问题，一百多年来一直是研究的对象。尽管进行了详尽的调查，但仍存在一系列悬而未决的问题。这种情况通常是不充分的，特别是在评估现有结构时，因为桥梁上部结构通常由于抗剪钢筋不足而在计算的抗剪承载力中存在缺陷，但没有显示出任何损坏迹象。本研究的目的是探讨边界条件和荷载条件对钢筋混凝土构件抗剪性能的影响。为了实现这一目标，剪切裂缝的几何形状和增长，发展的变形和流动的钢筋混凝土梁与不同的边界条件，荷载类型和剪力配筋率将系统地研究。该项目填补了从没有抗剪钢筋的构件中的剪切传递到具有足够抗剪钢筋的构件以建立完整桁架作用的过渡处的内部行为的基本知识的空白。建议的试验方案包括70个不同的静态系统和系统地改变剪切配筋率的梁试验，逐渐增加钢筋直径的箍筋，同时保持间距。由此产生的力的流动将通过先进的测量技术来表征。在从没有抗剪钢筋的构件到有抗剪钢筋的构件的过渡处，控制剪切传递机制，即直接支撑作用以及由压缩区、裂缝处理区、骨料联锁、销钉作用和抗剪钢筋提供的贡献，变化很大，如许多不同的剪切模型所示。然而，在过渡过程中的不同的剪切传递机制的量化仍在考虑中。由于这些方面还没有得到充分的研究，系统的调查的影响力和剪切阻力的流动是必要的。基于实验和理论工作计划，物理模型来描述钢筋混凝土构件的剪切性能将被开发和扩展。这些剪切模型将为物理上一致的设计概念提供背景，因此通常对具有不同边界条件的构件有效。有着相似的态度和互补的剪切建模方法，申请人和共同申请人之间的合作将非常有效地深入了解这一具有挑战性的问题，这具有很大的学术和实际意义。

Shear behavior is a complex and important problem in structural concrete and has been an object of research for more than 100 years. Despite elaborate investigations, a range of open questions still remains. This situation is generally not adequate, especially regarding the assessment of existing structures, as bridge superstructures often have deficits in the calculated shear capacity due to insufficient shear reinforcement, but do not exhibit any signs of damage. The goal of this research project is to characterize the effect of the boundary and loading conditions on shear behavior of RC members without and with small shear reinforcement ratios. To meet this goal, shear crack geometry and growth, development of deformations and flow of internal forces will be systematically investigated on RC beams with different boundary conditions, load types and shear reinforcement ratios. The project fills a gap in basic knowledge of the internal behavior at the transition from shear transfer in members without shear reinforcement to members with sufficient shear reinforcement to establish full truss action. The proposed experimental program comprises 70 tests on beams with different static systems and systematically varied shear reinforcement ratios by gradually increasing the bar diameter of the stirrups while maintaining the stirrup spacing. The resulting flow of forces will be characterized by advanced measu¬ring techniques. At the transition from a member without to one with shear reinforcement, the governing shear transfer mechanisms, i.e. direct strut action as well as contribution provided by compression zone, crack processing zone, aggregate interlock, dowel action and shear reinforcement, vary considerably, as demonstrated by the many different shear models. However, the quantification of the different shear transfer mechanisms in the course of the transition is still under consideration. Since these aspects have not been sufficiently studied yet, systematic investigations of the governing effects on the flow of forces and shear resistance are necessary. Based on an experimental and theoretical work program, physically based models to describe the shear behavior of RC members will be developed and extended. These shear models will provide background for design concepts that are physically consistent and, thus, generally valid for members with different boundary conditions. Sharing a similar attitude and having complementary approaches to shear modeling, the collaboration between the applicant and co-applicant will be very effective in gaining more insight into this challenging issue, which is of great academic and practical interest.