Fracture Mechanics Analysis Of Plain Concrete Beam With Crack

Concrete as a building material is indispensable to modern construction industry,and its abundant raw materials,low cost,simple process,light weight,high strength,function characteristics,the main materials of various structures become concrete in engineering field.Due to the heterogeneity of concrete material,lead to the main crack tip shows the micro crack zone of fracture process zone(referred to as FPZ),concrete is a quasi brittle material fracture behavior of its members or structures affected by the fracture process zone greatly.Therefore,it is of great engineering significance to study the failure law of the concrete members and structures under the static load.In order to study the concrete beam with crack under the load of crack tip micro crack propagation zone,the damage and fracture process of three point bending beam test was studied by digital image correlation method(DICM).Using the DICM technology with electrometric method can fracture process zone length,accurate measurement and calculation of crack opening displacement load,cracking load,failure load of the maximum value of mechanical parameters.In theory by using the finite fracture mechanics model theory(FFM)and the maximum circumferential normal stress criterion to correction(MMTS)of the maximum stress,stress intensity factor and the length of fracture process zone with the variation of crack size and high beam.In this paper,the main research contents and conclusions are as follows:(1)Through the digital image correlation method(DICM)is able to measure each specimen under different load corresponding to the crack opening displacement value,the fracture process zone length,the test results show that its value with the height of the specimen increases,decreases with the increase of initial seam height ratio,within the scope of the size of the experimental study showed a certain size effect.(2)Through the experimental analysis of different initial high ratio and height of concrete crack load,maximum load,fracture toughness,instability of toughness,fracture energy,the influence of the fracture parameters such as the loading point displacement,the results showed that the maximum bearing capacity affected by the size of the specimens,the fracture toughness and fracture energy basic remain unchanged.(3)Comparative analysis of finite fracture mechanics model based on(FFM)and the maximum circumferential normal stress criterion to correction(MMTS)data show that the theory: the maximum failure stress,the stress intensity factor decreases with the increase of the crack depth ratio,and the length of fracture process increases with the increase of crack depth ratio,and the three values were increased as the height.(4)The size of the fracture process zone is predicted by the modified maximum circumferential normal stress criterion,and the predicted value is close to that of the finite fracture model and has a good correlation with the experimental value.