【作者】 陶冶；

【导师】 赵艳华；

【作者基本信息】 大连理工大学 ， 结构工程， 2023， 硕士

【摘要】 混凝土断裂力学中,K_R阻力曲线理论是学科内的重要研究方向,在该理论中,借助虚拟黏聚力可以描述裂缝发展不同阶段的力学响应,进而完整反映裂缝扩展的全过程,增进了混凝土类准脆性材料的断裂基本特征研究进程,很好地解释了混凝土的增韧特性。本文在虚拟裂缝模型理论基础上,对现有试验数据进行了计算和分析,提出了一种基于损伤理论的K_R阻力曲线计算方法,主要研究内容与结论如下:（1）分别采用基于黏聚力模型和实用解析法对不同缝高比的弯曲梁试件进行了K_R阻力曲线计算,分析并探讨了现有理论的计算结果差异和不同加载形式对K_R阻力曲线的影响,结果显示黏聚力积分理论与解析法理论无明显差别,在现有理论框架下试件形式对K_R阻力曲线没有影响;（2）提出了一种基于损伤理论的混凝土K_R阻力曲线解析计算方法,将裂缝扩展解释为损伤的累积与微裂缝集聚,基于不同损伤本构模型和滑移场理论推导出损伤区应力应变表达。该方法在初始缝高比较小时具有很好的计算精度,需要的初始参量较少,避免了断裂能和P-CMOD曲线测算,实用性较强;（3）提出了基于损伤理论求得的混凝土极限K_R阻力K_dam,结果显示在不同条件下K_dam结果比较稳定,可以作为双K断裂模型的有益补充,分析对比了两种经典损伤本构模型在K_R阻力曲线计算中的结果,结果显示损伤本构模型对K_R阻力影响不大;（4）讨论了起裂韧度的解析算法,将损伤理论推广至全解析方法,分析研究了不同试件尺寸和强度等级对K_R阻力曲线的影响,结果显示试件尺寸的增加会使得损伤理论的计算结果更贴近实用解析法,强度等级的提高对损伤理论的计算准确性无明显影响,但K_dam值和K_R阻力曲线整体会随强度等级增加而增加。更多还原

【Abstract】 In concrete fracture mechanics,K_Rresistance curve theory is an important research direction,in which the mechanical response of different stages of crack development can be described with the help of virtual cohesion,and then the whole process of crack extension can be reflected completely,which enhances the process of studying the basic characteristics of fracture of quasi-brittle materials such as concrete and explains the toughening characteristics of concrete very well.In this paper,based on the theory of virtual crack model,the existing experimental data are calculated and analyzed,and a damage theory-based K_Rresistance curve calculation method is proposed,with the following main research contents and conclusions:（1）The resistance curves of bending beam specimens with different seam height ratios were calculated using the cohesive model-based and practical analytical methods,respectively,and the differences in calculation results between existing theories and the influence of different loading forms on the K_Rresistance curves were analyzed and discussed,and the results showed that there was no significant difference between the cohesive integral theory and the analytical method theory,and the specimen forms had no influence on the K_Rresistance curves under the existing theoretical framework;（2）An analytical calculation method of concrete K_Rresistance curves based on damage theory is proposed,in which the crack expansion is explained as the accumulation of damage and microcrack clustering,and the stress-strain expression in the damage area is derived based on different damage models and slip field theory.The method has good calculation accuracy when the initial seam height is small,requires less initial parameters,avoids fracture energy and P-CMOD curves measurement,and is more practical;（3）The ultimate resistance of concrete K_dambased on damage theory is proposed,and the results show that the results are more stable under different conditions,which can be a useful supplement to the double K fracture model,and the results of two classical damage principal structure models are analyzed and compared in the calculation of K_Rresistance curves;（4）The analytical algorithm of cracking toughness is discussed,and the damage theory is extended to the full analytical method.The influence of different specimen sizes and strength levels on the K_Rresistance curves is analyzed and studied,and the results show that the increase of specimen sizes will make the calculation results of damage theory closer to the practical analytical method.更多还原