Research On Softening Curve Of Hydraulic Concrete Based On Digital Image Correlation Method

Tensile softening curve of concrete fracture process zone is a very important standard to measure fracture characteristics of concrete,but so many years,scholars have failed to agree on the form of tensile softening curve.Because of the complexity on the concrete material and the limitations of the current test conditions,it's very difficult to directly study the fracture characteristics of the concrete,so theoretical model construction and experimental research have always been the hot topics in the field of engineering.Under the background,scholars have put forward various of tensile softening curve,and have given particular explanation from different angles for the fracture characteristics of concrete,but those softening curve have some advantages and limitations.So,the inverse analysis that just need relatively low experimental condition have been widely used in the theoretical study of concrete fracture mechanics in many universities.The main work of this paper includes the following aspects:(1)Doing the three-point bending fracture test based on the digital image correlation method(DICM),and observing the crack propagation process of specimen.Based on the process of the test,studied the law of crack development,calculated the crack mouth opening displacement(CMOD)and recorded the load of the whole text process.All this provided the base of the data for calculating the whole field displacement and the long of the fracture process zone(FPZ).(2)Assuming function of tensile softening curve is exponential,according to the work of Huang Caizheng,using fictitious crack model witch fracture process zone of concrete is linear displacement distribution to simulate the curve of P-CMOD.So that can analyze the fracture process of concrete and the cohesive force distribution.All this provided a model for the inverse analysis.(3)Using the genetic algorithm(GA)to fit curve of model P-CMOD and curve of test P-CMOD,and obtained relative parameters of tensile softening curve.All work have verified the exactness of the model,and have used MATLAB software to edit relevant program for the study.