基于三维细观分析方法的CFRP加固无腹筋混凝土梁剪切强度尺寸效应研究

以CFRP侧贴加固无腹筋钢筋混凝土悬臂梁为研究对象，从细观角度出发，考虑混凝土细观非均质性及CFRP-混凝土之间的相互作用，建立了单调加载下CFRP侧贴无腹筋钢筋混凝土悬臂梁三维细观尺度数值分析模型。通过仅改变CFRP条带的厚度来改变CFRP的配纤率，进而以CFRP的配纤率为主导参数，并且在之前试验工作的基础上，扩展模拟了尺寸和配纤率对梁的剪切破坏机理和失效模式的影响，研究了外贴CFRP加固钢筋混凝土悬臂梁剪切破坏尺寸效应行为。结果表明: CFRP侧贴加固无腹筋钢筋混凝土梁的名义剪切强度尺寸效应明显，CFRP布加固对小尺寸梁贡献最大，其有效性随着梁尺寸的增加而减小； 配纤率的增大提高了悬臂梁的名义抗剪强度，但同时也削弱了抗剪强度的尺寸效应； 当配纤率较大时，峰值剪切应力的增长趋势明显减缓，即层数过多时，加固效果不明显。

Study on size effect on shear strength of CFRP-strengthened concrete beams without web reinforcement based on 3D meso-scale analysis method

Taking reinforced concrete cantilever beams strengthened by CFRP side bonding as the research object, and considering the meso-heterogeneity of the concrete and the interaction between the CFRP and concrete, a three-dimensional meso-scale numerical analysis model of CFRP side bonding strengthened reinforced concrete cantilever beams without web reinforcement under monotonic loading was established. In this study, the size of the CFRP fiber ratio was realized by changing the thickness of the CFRP strip, and the CFRP fiber ratio was considered as the dominant parameter. Moreover, based on the previous experimental work, the influence of the size and fiber ratio on the shear failure mechanism and failure mode of RC cantilever beams strengthened with CFRP was studied, and the shear failure size effect of RC cantilever beams strengthened with CFRP was studied.The results show that nominal shear strength size effect of reinforced concrete beams without web reinforcement is obvious, and CFRP sheet reinforcement contributes the most to small-sized beams. The effectiveness decreases with an increase in beam size. The increase of fiber ratio improves the nominal shear strength of cantilever beams, but it also weakens the size effect of shear strength. When the fiber ratio is high, the increase of peak shear stress is obviously slowed down, that is, the reinforcement effect is not obvious when an overly large number of layers are used.