Study On Calculation Method Of Concrete Stochastic Fracture And Characteristics Of Process Zone

Defects such as randomly distributed meso-cracks existing in the concrete structure are aggregated and developed when subjected to a load,which can easily lead to structural instability and damage.As a quasi-brittle material,the important feature of nonlinear fracture behavior of concrete is the existence of a fracture process zone at the crack front that is relatively large and cannot be ignored.Under normal circumstances,the formation mechanism of the fracture process zone of concrete is very complicated,but there has been less research on the stochastic of the fracture process zone in the past.Therefore,studying the stochastic characteristics of the evolution of the concrete fracture process zone is conducive to exploring the real cause of concrete structure damage.It has important guiding significance for the analysis and repair of cracks in the concrete structure during construction and operation.This article mainly carried out the following research:(1)Based on the concrete fracture and stochastic damage evolution model,the stress intensity factor and crack opening displacement in the crack propagation process of concrete were solved.Based on the crack initiation toughness expansion criterion,the numerical simulation of the whole process of stochastic fracture of concrete was achieved by numerical iterative method,and the theoretical characteristics of the fracture process area of concrete were obtained.The crack propagation of different types of specimens,such as ordinary concrete wedge-split tensile test specimens and dam concrete and wet-screen concrete three-point curved beam specimens,is simulated.The practicability of the method in this paper is verified by comparing the calculated concrete fracture property results with the experimental measured values.(2)Combined with the probabilistic method,a stochastic acquisition method of concrete softening curve is proposed.The whole process of stochastic fracture of concrete is simulated,and the characteristics of the stochastic fracture process area of concrete are calculated.The relationship between the stochastic crack opening displacement and the stochastic cohesion distribution with the crack growth is obtained.The influence of cohesive force distribution and the length of the critical fracture process zone further calculated the stochastic energy consumption curve of concrete.Based on the stochastic fracture process zone analysis method,the critical fracture process zone characteristics of ordinary concrete wedge-split tensile test specimens and wet-screen concrete three-point curved beam specimens were calculated.The results show that the cohesion curve shows a non-linear distribution.As the cracks expand,the range of cohesive force distribution gradually increases.When the cracks expand to a certain degree,that is,after the cracks are completely cracked,the range of cohesive force distributions decreases.As the load increases and the cracks gradually expand,the stochastic crack opening displacement curve shows a trend of gradually changing from a non-linear distribution to a linear distribution.The critical stochastic cohesion distribution range,critical stochastic crack opening displacement,and critical stochastic fracture process zone length all increase with the increase of specimen size.When the specimen size is increased to a certain extent,the increase in the length of the critical stochastic fracture process zone gradually becomes insignificant.As the size of the specimen increases,the stochastic energy consumption tends to increase,and as the cracks expand,the stochastic energy consumption curve increases.(3)Based on the crack initiation toughness criterion and the Paris displacement formula,a calculation model for the whole process of concrete fracture under the action of hydrostatic pressure was established,and the effects of peak load and critical crack opening displacement on the load-crack opening displacement curve were analyzed.By introducing a stochastic softening curve,a calculation model of the relevant characteristics of the stochastic fracture process area of concrete under the action of hydrostatic pressure is established,and the stochastic characteristics of the concrete fracture process area under different water pressure are calculated.The results show that at the same initial crack length,the peak load and critical crack opening displacement of the specimen decrease.The greater the water pressure,the more obvious the damage to the material.With the increase of hydrostatic pressure,the ratio of the average value of the length of the critical stochastic fracture process zone to the average value of the critical stochastic fracture process zone without water pressure gradually decreased,but the decrease gradually decreased.