Experimental And Theoretical Study On The Dynamic Properties Of Concrete

Study on the dynamic behavior of concrete is one of the weakest links for the design and seismic safty evaluation of large-scale concrete structures, such as bridges, arch dams and so on. This paper attempted to experimentally and theorecitally study the dynamic properties of concrete and its dynamic failure mechanism.The uniaxial properties of concrete in both dynamic tensile and compressive loadings were investigated systematically. The rate-dependent deformation characteristions were studied along with the strength;the elastic modulus, Poisson ratio critical strain and energy absorption capability were tested over a rather wide range of strain rate. The results were analyzed and formulas were proposed to describe the complete stress-strain curves at varying strain rate. The fracture process of concrete in dynamic loadings was studied.The dynamic behaviors of concrete under different environment conditions were investigated detailedly. Environment factors, such as temperature and moisture state had an important influence on the strain-rate sensitivity of concrete. The effect of these parameters was examined based on the results of both tensile and compressive tests. Furthermore, the mechanism of rate-dependent behavior of concrete was analyzed and a physical explanation for the strain-rate enchancement was proposed.Considering the stress state of the large-scale concrete structures when exposed to earthquake, the dynamic properties of concrete were tested in tensile cyclic loadings with different frequencies, amplitude increment rates and initial static load intensity. The strength and deformation characteristics were also studied. The effect of initial static load on the strain-rate sensitivity of concrete in compression was discussed and an equation was proposed to characterize the influence of initial load intensity on the dynamic strength. The deformation was also analyzed. Based on the artificial neural network method, a new way to analyze the test data was suggested.Dynamic properties of concrete in biaxial dynamic loadings were studied. Two cases of loading types were adopted: one was biaxial proportional dynamic loading and the other was axial dynamic loading with one-side constant confining pressure. The strength, deformation and crack pattern with strain rates were analyzed systematically. Strength formula were established for the failure of concrete subjected to different types of biaxial loading and the results from the formula were proved to match the test results farely well..Triaxial compression tests were also carried out on cubic specimens. The specimens were kept in triaxial stress states.In the axial direction it was applied with different strain-ratecompressive loadings and the confining pressure was maintained constant during the loading process. The change in the dynamic strength along with confining pressure was discussed and a dynamic strength formula was proposed to reflect the effect of confining pressure and the effect of strain rate on the ultimate strength of concrete in triaxial stress states. The deformation characteristics of concrete under different confining pressures and different strain rates were analyzed.