Investigation On The Measurement Of Mechanical Behavior Of Concrete Under Static And Dynamic Loadings At Normal Temperature

Concrete is a kind of engineering composite material, which is broadly used in military and civil structures. The static performance on concrete can not be provided to estimate the variation of concrete under high strain rates concerning dynamic loads. Furthermore, higher loading velocity can not be achieved by static loading test equipments which is commonly used now a days. Therefore, a special testing device should be applied to it. In the present paper, with the aid of universal material test machine and split Hopkinson press bar, a relative simple testing method has been established for the testing of dynamic plane strain fracture toughness in concrete.Firstly, by the compression test in concrete under different strain rates, concrete has been determined as rate-sensitive material. Moreover, under quasi-static loads, Young's Modulus before the damage limit can be obtained by Instron 4505 universal material test machine and static resistance strain meter, suppose that Young's Modulus of concrete will not vibrate with the variation of strain rate. When impact compression test is exerted, the pulse shaper has been used to regulate the incidence wave, so that the stress gradient will not be significantly high and the results is acceptable.Then, by introducing Instron 4505 universal material test machine and 37mm split Hopkinson press bar to three point bending test, and with the application of experimental-numerical method, tri-dimensional model has been established by FEM software Ansys, to operate transient analysis, and the response curves of stress intensity factor-time can be achieved through opening displacement of fracture. Sticking resistance strain gage to the crack tip field, cracking time of specimen can be obtained. Thus, the dynamic plane strain fracture toughness K_Id can be determined. Compared with static plane strain fracture toughness K_Ic, we can conclude that concrete is more liable to crack under dynamic load.The testing method established in this paper can provide some useful references to engineering design or directional demolishing blasting for structure engineer. Valuable advices and suggestions will be highly appreciated.