混凝土裂缝损伤断裂分析及试验研究

发布时间：2018-04-16 08:03

本文选题：混凝土 + 损伤　；参考：《河北工业大学》2015年硕士论文

【摘要】：混凝土的裂缝问题一直是土木、水利科学技术界和工程界极为关心的课题。混凝土裂缝的产生是损伤演化到一定程度的结果,在断裂过程中,损伤与断裂相互耦合。因此,研究混凝土的损伤断裂特性,首先应弄清楚其损伤断裂机理。本文结合国家自然科学基金(51309073)对混凝土裂缝断裂及损伤问题进行深入研究,提出了混凝土损伤本构模型,采用理论分析及试验方法对混凝土裂缝损伤断裂过程进行了研究。论文的主要工作及结论如下:1、本文基于对几种典型混凝土损伤本构模型的分析比较及混凝土损伤理论,提出了一种新的混凝土损伤本构模型,并通过实例与已有损伤模型进行了比较,验证了本文模型的正确性及有效性。2、本文基于williams级数展开式缝尖渐近解,推导了混凝土缝尖断裂过程区长度的计算公式及线弹性状态与损伤状态下I型裂纹缝尖的位移场、应力场,并通过实例进行了验证。结果表明,裂缝临界断裂过程区的长度随着试件高度及初始缝长的增大而增大,随着试件初始缝高比的增大而减小;级数展开式的常数项及若干高阶项对缝尖应力场、位移场的影响可以忽略,缝尖的应力场可以由奇异项代表的应力强度因子控制。3、将本文提出的损伤本构模型推广至混凝土三点弯曲梁试件、紧凑拉伸试件及楔入劈拉试件,计算三种试件裂缝尖端的损伤值及缝尖的损伤应力。结果表明在峰值荷载作用下三种试件裂缝尖端的损伤程度与外荷载、试件尺寸及初始缝高比均有关。4、数字照相量测技术是基于物体表面的图像灰度分析,进而获得观测域内各点的运动和变形信息的一种新型观测方法。本文采用数字照相量测相关技术测量了混凝土三点弯曲梁构件在裂缝扩展过程中缝尖各点的应变及断裂过程区的长度等。结果显示试件裂缝扩展轨迹与断裂时的裂缝轨迹吻合良好,且断裂过程区的长度与理论值比较接近,证明了数字照相量测相关技术可以用来测量混凝土试件断裂过程区长度。
[Abstract]:The crack problem of concrete has always been a subject of great concern to civil engineering, water science and technology and engineering.The formation of concrete cracks is the result of damage evolution to a certain extent. In the process of fracture, the damage and fracture coupling each other.Therefore, to study the damage and fracture characteristics of concrete, it is necessary to find out the damage and fracture mechanism of concrete.In this paper, combined with the National Natural Science Foundation of China 51309073, the fracture and damage of concrete cracks are deeply studied, and the damage constitutive model of concrete is put forward, and the process of crack damage and fracture of concrete is studied by theoretical analysis and test method.The main work and conclusions are as follows: 1. Based on the analysis and comparison of several typical concrete damage constitutive models and concrete damage theory, a new concrete damage constitutive model is proposed in this paper.The validity and validity of the model are verified by comparing the model with the existing damage model. The asymptotic solution of the crack tip based on the williams series expansion is presented in this paper.The formula for calculating the length of fracture process zone of concrete joint tip and the displacement field and stress field of mode I crack tip under linear elastic state and damage state are derived and verified by an example.The results show that the length of critical fracture zone increases with the increase of specimen height and initial fracture length, and decreases with the increase of initial fracture height ratio.The effect of displacement field can be neglected, and the stress field of joint tip can be controlled by the stress intensity factor represented by singular term. The damage constitutive model proposed in this paper is extended to concrete three-point bending beam specimen, compact tensile specimen and wedge splitting tensile specimen.The damage values at the crack tip and the damage stress at the crack tip of the three specimens were calculated.The results show that the damage degree of the crack tip of the three specimens under the peak load is related to the external load, the size of the specimen and the ratio of initial joint height. The digital photography technique is based on the image grayscale analysis of the surface of the object.A new method for obtaining the information of motion and deformation of points in the observational domain is presented.In this paper, the strain of the crack tip and the length of the fracture zone during the crack propagation of the concrete three-point bending beam members are measured by digital photographic correlation technique.The results show that the crack propagation trajectory of the specimen agrees well with the fracture track, and the length of the fracture process zone is close to the theoretical value. It is proved that the digital photographic measurement correlation technique can be used to measure the fracture process zone length of concrete specimen.
【学位授予单位】：河北工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU755.7

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