Study On The Tensile Softening Constitutive Relationship Of Dam Concrete And Wet-screening Concrete

The fracture process zone of concrete has softening behavior. According to the Fictitious Crack Model, the constitutive relationship of the cracking zone can be described by stress-crack opening width curve( σ-w),namely tension softening curve. The tensile softening relation( σ-w curve) of concrete is one of important indicators for evaluating the fracture behaviors of concrete. The macroscopic fracture responses of concrete structure can be predicted by numerical simulations with σ-w curve(be hereafter referred to as Softening Curve).The direct tension(DT) tests were performed on dam concrete specimens employed the construction mix proportions of the Three Gorges dam project concrete. There are 8 groups or a total of 40 DT dam and wet-screening concrete specimens with different strength and coarse aggregate size. Based on the DT test data and analysis of concrete fracture mechanics, the softening curves and their expressions were obtained. There are 14 groups or a total of 56 wedge-splitting(WS) specimens employed the same raw materials and mix proportions as the corresponding DT specimens. The load-crack mouth opening displacement(P-CMOD) curves were tested by WS tests, and the softening curves of concrete were achieved by the FEM program made by the inverse analysis method based on the improved evolutionary algorithm. The comparison between the softening curves by inverse analysis method and those by direct tension method were made in order to verify the validity of the determination of softening curve by inverse analysis method.Because of the limitations of specimen size and test set-up, we always use wet-screening concrete specimens instead in the mechanical property simulate measurement of dam concrete. However, there are few studies of softening property between wet–screened concrete and dam concrete. So the present research conducted comparative study on the relationship between the softening curves of wet–screened concrete and that of dam concrete, and discussed the effect of the aggregate size and water-cement ratio to softening parameters. It can provide a reference to future studies on the softening behavior of dam concrete and to the crack control of dam concrete.