Damage Fracture Analysis In Concrete With Crack

The crack problem has always been concerned by civil engineering and water conservancy science and technology and engineering in concrete. The cracks of the concrete are the result of damage evolution to a certain extent. In the process of fracture, damage and fracture mutual coupling. Therefore, it is the first to know its damage fracture mechanism to study the damage fracture properties of concrete. Combining with the national natural science foundation of China(51309073) to conduct the thorough research to the concrete crack fracture and damage problem.the damage constitutive model is proposed in this paper, and crack damage fracture are studied using theoretical analysis and experimental method in concrete. The main work and conclusions are as follows:1. Based on several different analysis and comparison of several kinds of typical damage constitutive model of concrete and the concrete damage theory, this paper proposes a new damage constitutive model of concrete, and verify the correctness and effectiveness of the model by comparing with the existing damage model Through the instance.2. Based on the asymptotic series expansion of Williams on concrete crack tip, the calculating formula of fracture process zone length and displacement field and stress field of type I crack tip under linear elastic state and damage state are deduced, which is verified by an example. Results show that,under peak stress fracture process zone length increases as the specimen height and initial crack length, and decreases along with the increase of the initial crack height ratio of the specimen; the influence of the constant term and number of high-order items of series expansions on displacement field and stress field of concrete crack tip can be ignored,the stress field of concrete crack tip can be controlled by the singular term stress intensity factor.3. Promote damage constitutive model proposed in this paper to concrete three-point bending beam specimens, compact tension specimen and wedge splitting specimen, and calculate the damage value and the damage stress of three kinds of specimen on crack tip. Results showed that under peak load the damage degree and external load, specimen size and initial crack height ratio on the crack tip of the three specimens are related.4. Digital photographic measurement technology is a new type of observation method,which is based on image of the object surface gray scale analysis, to obtain the movement and deformation information of each point in the observational domain.Measured by digital photography measurement technology in this paper, in the fracture process, the strain and fracture process length at various points of the concrete three-point bending beam component, etc. Results show that the trajectory of specimen fracture coincides well with fracture of crack and fracture process zone length are similar with the theoretical value, proved that digital photography measurement technology can be used to measure the fracture process zone length of concrete specimen.