Dynamic flexural strength of concrete under high strain rates

In a split Hopkinson pressure bar bending test on quasi-brittle materials, the specimen maintains a non-equilibrium state and failure occurs before the response of the supports (the transmission bars) appears, as would occur in a support-free impact test. This paper investigates principally the dynamic response of un-notched concrete beams subjected to three-point bending load. To guarantee the accuracy of experimental results analysis, a dynamic response analysis is introduced in the investigation. This assumes that the specimen fractures before the support reaction appears. The long beam model is used in this paper to study the dynamic bending behaviour of specimens that fail after a very short duration of loading. The test results show that the dynamic flexural tensile strength of concrete is strain rate sensitive, and the dynamic increase factor is linearly proportional to the strain rate. Finally, the finite-element software LS-Dyna is used to simulate the failure pattern of specimens in a dynamic bending test. The simulation results verify the validity of the long beam model in processing the experimental data.