Wang Zhanliang, Zhang Wei, Huang Yiqun
School of Civil Engineering, Fujian University of Technology, Fuzhou 350118, China.
Materials (Basel). 2023 Sep 20;16(18):6311. doi: 10.3390/ma16186311.
In this paper, a series of experimental and numerical studies were carried out to investigate the effect of multiple cracks on concrete fracture behavior. Seven groups of double-crack concrete three-point bending (TPB) experiments with different crack lengths and different crack distances were carried out. The experimental results showed that the bearing capacity of double-crack specimens was slightly larger than the standard specimen with one central crack. Additionally, with an increase in the second crack length or with a crack distance reduction, the concrete's bearing capacity increased correspondingly. Based on the experiments, a numerical meso-model was developed based on applying cohesive elements. The aggregate, mortar, interface transition zone (ITZ), and potential fracture surfaces were explicitly considered in the model. In particular, cohesive elements were used to characterize the mechanical behavior of the ITZ and potential fracture surfaces. A modified constitutive concrete model was developed by considering the potential fracture surfaces' damage relation and friction effect. The accuracy of the developed meso-model was validated through a comparison between simulation and experiments. Based on meso-models, the influence of multiple cracks on the concrete bearing capacity was investigated by analyzing the energy evolution. The analysis results showed that the bearing capacity has a linear relation with the proportion of mode II energy consumption during the fracture process, which explains why specimens with multiple cracks have a slightly larger bearing capacity than the standard specimens. In summary, this study has found that in three-point bending fracture tests primarily characterized by mode I fractures, the presence of multiple cracks near the main crack slightly enhances the load-bearing capacity of the specimens. This is attributed to a slight increase in internal energy dissipation associated with the presence of these multiple cracks.
本文开展了一系列试验和数值研究，以探究多条裂缝对混凝土断裂行为的影响。进行了七组不同裂缝长度和不同裂缝间距的双裂缝混凝土三点弯曲（TPB）试验。试验结果表明，双裂缝试件的承载能力略大于具有一条中心裂缝的标准试件。此外，随着第二条裂缝长度的增加或裂缝间距的减小，混凝土的承载能力相应提高。基于试验，应用粘结单元建立了一个数值细观模型。该模型明确考虑了骨料、砂浆、界面过渡区（ITZ）和潜在断裂面。特别是，使用粘结单元来表征ITZ和潜在断裂面的力学行为。通过考虑潜在断裂面的损伤关系和摩擦效应，建立了一种改进的混凝土本构模型。通过模拟与试验的对比验证了所建立细观模型的准确性。基于细观模型，通过分析能量演化研究了多条裂缝对混凝土承载能力的影响。分析结果表明，承载能力与断裂过程中II型能量消耗的比例呈线性关系，这解释了为什么多裂缝试件的承载能力略大于标准试件。总之，本研究发现，在以I型断裂为主的三点弯曲断裂试验中，主裂缝附近多条裂缝的存在会略微提高试件的承载能力。这归因于这些多条裂缝的存在使内部能量耗散略有增加。
