Study Of Thickness Dependent Size Effect On Concrete Fracture And Modified Narrow Strip Fracture Model

Fracture mechanics of concrete is a very practical mechanics course,which is developed based on general fracture mechanics.The size effect of fracture parameters and the characterization of fracture process zone are two important theoretical problems,which are the keys to establish effective fracture criterion and realize the engineering application.Considering the inadequate of research on thickness dependent size effect of fracture parameters of concrete,an experimental study is investigated using three-point bending beams,which belongs to the work of RILEM TC265-TDK Technical Committee:Testing methods for determination of double-K criterion for crack propagation in concrete.During the study,the double-K fracture toughness and the fracture energy of 29 specimens(5 groups,with the range of thickness from 100mm to 300mm)is tested and calculated,the relationship between the fracture parameters and the thickness of specimens is evaluated quantitatively,and the rationality of the standard calculation method is also discussed.It is found that there exists no remarkable thickness dependent size effect for the fracture parameters of concrete.The experimental results are also analyzed based on the linear elastic formula of fracture toughness,the Weibull size efFect and three dimensional inspection.Additionally,in view of the simple parsing and general application,a modified narrow strip model for concrete is put forward based on the early model and other achievements of classical fracture theory such as double-K fracture model.This new approximate model has the advantage of clear concept and simple calculation,which has been verified by above tests and could be used as an alternative of engineering application.