A Study On The Stress Intensity Factor And Fracture Process Zone Of A Crack Vertical To The Interface Between Different Materials

At present,the steel and concrete composite beam has been widely used in buildings and bridges,but in the negative moment area of continuous beam,concerned pull concrete slab cracking and steel and concrete interface shear slip is remain a matter of universal concern in the engineering circles and academic circles.This paper studies the problem crack vertical to the interface,using the finite element method to calculate stress intensity factor,the fracture process zone is applied to the numerical simulation of crack and interface slip of steel and concrete composite beams.The main research contents and conclusions are as follows.(1)The basic theory of fracture mechanics is expounded,and the calculation method of stress intensity factor is briefly introduced,and the formula of stress intensity factor is deduced by solving the stress singularity characteristic equation of bimaterial vertical interface crack.(2)The vertical to the interface crack model carrried by the finite element simulation,and the stress intensity factors of a single material are calculated and analyzed by theoretical and numerical methods,it is concluded that compared with the ordinary element method,the results of the singular element method are more accurate and closer to the theoretical values.The numerical method is further applied to the calculation of stress intensity factor of bimaterial vertical interface crack of tension and bending.It is simulating analysised that the stress intensity factor of crack vertical to the interface increase with the distance between the crack tip and the interface decreases and the increase of elastic modulus of cracked material.It also increases with the increase of Poisson's ratio of the crack material,but the influence is not significant.(3)Based on the virtual crack model and the Duan-Nakagawa model,considered the softening effect of concrete under tensile strain in the fracture process zone,two models are established respectively within or without considering the interface shear slip,to numerical simulated a steel and concrete composite beam subjected to bending action is carried out.The analysis results show that with the increase of tensile strength of concrete and the length of fracture process zone increases and interfacial shear slip strength enhancement the opening displacement of the crack mouth and the deflection of the beam decrease.