Experimental Research On Rate Effect And Failure Mechanism Of Concrete Under Different Environment Or Loading

Due to the strength, stiffness and ductility of the concrete structure will be subjected to the influence of loading rate. Therefore, rate effect and failure mechanism of concrete is one of the key factor in seismic safety evaluation. This paper attempted to experimentally and theorecitally study rate effect of concrete and its dynamic failure mechanism.The dynamic compression test of concrete was carried out under water saturated, loading history and biaxial compression by triaxial apparatus. And analyzed the destruction mechanism of concrete CT images. completed total247specimen loading test, selected168valid data sets for analysis. The main research contents are as follows:First, the rate effect of concrete was investigated detailedly under water saturated. Uniaxial compression test and triaxial compression test of two confining pressure(4MPa>8MPa) of concrete under condition of atmospheric natural moisture and water saturated has been carried out at four loading rates(10-5/s、5×10-5/s、10-4/s、5×10-4/s) in this paper.The physical and mechanical parameters such as the elastic modulus, the strength, the deformation were studied under the different strain rate and confining pressure. This paper gave a definite conclusion about the influence extent and rule of rate effect of concrete under water environment and established triaxial strength rate effect empirical formula.Second, the rate effect of concrete was investigated detailedly under different load types and loading history. To study the dynamic uniaxial compression test of concrete under static load and cyclic loading history at there different strain rates. Comparatively analyzed the mechanical properties such as peak stress, peak strain and elastic modulus of concrete under different static loadings history and strain rate. The mechanical properties of concrete were analyzed under different cyclic amplitude, cyclic frequency and strain rate. The influence of concrete strength was weakened by loading history at high strain rate (10"3/s). Modulus of elasticity has reached the maximum when static loading history of value is60%of the ultimate compressive strength. The degradation of concrete strength under cyclic loading historyis more clear at low strain rate (10-3/s).Third, the rate effect of concrete was investigated detailedly under uniaxial and biaxial compression. Compression tests of concrete samples of large scale under uniaxial and biaxial compression at three loading rates (10-5/s,10-4/s,10-3/s) and four kinds of lateral stress levers (OMPa,2.8MPa,5.6MPa,8.4MPa). And the mechanical property of concrete as uniaxial compression strength, deformation characteristic and elastic modulus under uniaxial compression or different lateral stress levers were analysed, gave a clear conclusion about the variety regulation.Fourth, the destruction mechanism of concrete was analyzed according to the images obtained from CT. Through the CT real-time of concrete specimen cross section at different loading stages11scanning and peripheral section and the section in the middle of the scan.concrete specimen cross-sectional was scaned11times at different loading stages and the ninth, tenth, eleventh loading stages were scaned from outside to inside. This paper gave a clear description of the water saturation concrete dynamic damage and failure pattern from the mesoscopic level and explainde the damage and failure mechanism.