In concrete structures, opened cracks contribute significantly to the transfer of shear and normal stresses through the contact forces occurring between fractured surfaces. Such contact forces are due to protruding asperities, engaged by interlocking and friction. In this paper, the role played by roughness on shear resistance is investigated numerically. First, micro computed tomography and digital microscope measures of concrete surfaces are used to validate a novel numerical generator of realistic cracked concrete surfaces. Secondly, a contact solver based on the boundary integral approach allows an extremely fine description of typical cracked surface topologies. Roughness changes drastically the predictions, so that the shear resistance computed numerically matches the prior experimental results reported in the literature. The proposed model does not need any fitting procedure, making it a reliable and physically based method for predicting shear transfer phenomena in concrete. An empirical power-law predicting the shear resistance in concrete is a direct outcome, which accounts for micro-scale roughness and aggregate distribution.

在混凝土结构中，打开的裂缝通过断裂表面之间发生的接触力对剪切应力和法向应力的传递有很大贡献。这种接触力是由于突出的凹凸不平，通过互锁和摩擦接合。在本文中，数值研究了粗糙度对剪切阻力所起的作用。首先，混凝土表面的显微计算机断层扫描和数字显微镜测量用于验证真实裂纹混凝土表面的新型数值生成器。其次，基于边界积分方法的接触求解器可以对典型的裂纹表面拓扑结构进行极其精细的描述。粗糙度会极大地改变预测，因此数值计算的剪切阻力与文献中报道的先前实验结果相匹配。所提出的模型不需要任何拟合程序，使其成为预测混凝土中剪切传递现象的可靠且基于物理的方法。预测混凝土抗剪强度的经验幂律是一个直接结果，它解释了微观粗糙度和骨料分布。