Shear behavior of RC members without shear reinforcement – development of a consistent experimental, analytical and numerical characterization methodology

在过去大量的努力已经投入到分析无抗剪钢筋混凝土板和梁的抗剪性能。尽管已经取得了相当大的进展，但对剪切带行为的一致描述仍然缺失。这一事实可以通过科学界关于控制剪切行为的现象的确切作用、它们的充分量化和它们在建模方法中的适当表示的持续争论来证明。提出的研究的主要目的是通过开发一个新的理论和实验框架来填补这一空白，该框架可以彻底描述剪切破坏过程。理论框架将始终如一地捕捉剪切破坏的基本机制，包括(1)裂纹局部化，(2)裂纹扩展，(3)由于骨料联锁引起的裂纹面压敏摩擦，(4)粘结行为，(5)销钉作用，以及(6)压缩区的非线性材料行为。所提出的建模策略将结合沿临界剪切裂纹截面的解析模型（一级）和具有离散裂纹表示的剪切区丰富有限元模型（二级）。通过用不同程度的细节和不同数量的计算工作量来表示剪切区行为所涉及的基本机制，将有可能在模拟的准确性和效率之间取得平衡。建模策略的成功实施将导致剪切区行为的非常有效的模拟，包括在整个加载过程中对裂纹扩展的准确预测和相互作用的剪切传递贡献（残余拉应力，骨料联锁，销钉作用和压缩区剪切）的量化。已开发的分析和数值模型的校准将使用具有一致组件测试集的测试程序进行。除了现有的和标准化的测试装置用于确定压缩、应变软化、脱粘和钉作用的本构规律外，还将开发一种新的测试装置，用于表征骨料沿裂纹面的互锁。两级模型的验证将由一组使用高分辨率测量技术（DIC）监测的钢筋混凝土梁试验提供。通过将结构混凝土和数值力学两门学科的最佳实践结合起来，本研究将大大提高我们对剪切带行为的认识。从长远来看，它将为结构设计方法提供良好的基础，降低材料消耗，延长使用寿命，提高工程结构的可靠性。

Large efforts have been devoted in the past to analyze the shear behavior of RC slabs and beams without shear reinforcement. Albeit a considerable progress has been achieved, a consistent description of the shear zone behavior is still missing. This fact can be documented by an ongoing dispute in the scientific community on the exact role of phenomena governing the shear behavior, on their adequate quantification and their appropriate representation in modeling approaches.The major objective of the proposed research is to fill this gap by developing a new, theoretical and experimental framework that can thoroughly describe the shear failure process. The theoretical framework will consistently capture the elementary mechanisms involved in the shear failure, including (1) crack localization, (2) crack propagation, (3) pressure-sensitive friction of the crack faces due to aggregate interlocking, (4) bond behavior, (5) dowel action, and (6) nonlinear material behavior in the compression zone. The proposed modeling strategy will combine analytical models of the cross section along the critical shear crack (Level I) and enriched finite element model of the shear zone with discrete crack representation (Level II). By representing the elementary mechanisms involved in the shear zone behavior with a different degree of detail and different amount of computational effort, it will be possible to balance trade-off between accuracy and efficiency of the simulation. Successful implementation of the modeling strategy will lead to a very efficient simulation of the shear zone behavior including the accurate prediction of the crack propagation and the quantification of the interacting shear transfer contributions (residual tensile stress, aggregate interlock, dowel action and shear in compression zone) during the entire loading history.Calibration of the developed analytical and numerical models will be performed using a test program with a consistent set of component tests. Besides existing and standardized test setups used to identify the constitutive laws for compression, strain softening, debonding and dowel action, a new test setup for the characterization the aggregate interlock along the crack faces will be developed. The validation of the models at both levels will be provided by a set of reinforced concrete beam tests monitored using high-resolution measuring techniques (DIC).By bringing together the best practices of two disciplines, i.e. structural concrete and numerical mechanics, this research will significantly enhance our insight into the behavior of shear zone behavior. In the long run, it will provide a sound basis for structural design methods with reduced material consumption, extended service life, and increased reliability of engineering structures.