Study On The Strength And Deformation Of Concrete Under Multiaxial Stress After High-temperature Or Freeze-thaw Cycling

The mechanical characteristic of concrete will be damaged in some severe environments such as freeze-thaw cycling and high temperature, etc. At present, most experiments and theory studies in this field no matter domestic or overseas are focused on uniaxial stress condition. Besides, correlative references are scarce. Actually considerable structural elements such as shear wall, dam, bridge, safety shell of nuclear reactor, offshore platform and so on, are generally working under multiaxial stress condition. But report about experimental research on mechanical behavior of concrete under multiaxial stress subjected to high temperature or freeze-thaw cycling is difficult to be seen. So, corresponding experimental researches and theory studies were made in this paper based on the project of educational department of Liao Ning province science foundation "Research on failure criterion and durability of concrete in severe environments"(2023901023). Main researchful contents in this paper are as follows:1) Experiments on strength and deformation of concrete under uniaxial compression, tension after high temperature are made. The influence of high temperature on mechanical behavior of concrete was analyzed. The relationship between temperature and uniaxial compressive strength, unaxial tensile strength, corresponding strain, elastic module is proposed from experiments by regression. And the result of microcosmic configuration of concrete subjected to various temperatures tested by electron microscope is reported in this paper.2) Experiments were made on strength and deformation of concrete under uniaxial compression and tension after freeze-thaw cycling. The effect of freeze-thaw cycling on mechanical behavior of concrete is studied. The equation of cycles of freeze-thaw cycling and respective strengths, strains, elastic modules of concrete under uniaxial compression and uniaxial tension were obtained by regression. The result of microcosmic configuration of concrete subjected to various cycles of freeze-thaw cycling tested by electron microscope is shown in this paper.3) Experimental researches were made on strength and deformation of concrete under biaxial compression with equal proportion after high temperature or freeze-thaw cycling. The failure envelope of concrete subjected to freeze-thaw cycling is obtained. The relationship between strength, strain of concrete and temperature, cycles of freeze-thaw cycling, stress ratio are studied. Respective failure criterions in principal stress space and principal strain space are proposed.4) On the foundation of experiment, researches on strength and deformation of concrete under biaxial non-proportional compressions after high temperature or freeze-thaw cycling were carried out. The relationship between strength, strain of concrete and temperature, cycles of freeze-thaw cycling, values of constant lateral compression is analyzed. Based on test data, respective failure criterions in principal stress space are proposed.5) Experiment researches on strength and deformation of concrete under biaxialAbstractstension-compression after high temperature or freeze-thaw cycling were made. The effect of high temperature, cycles of freeze-thaw cycling, stress ratios on the strength and strain of concrete is analyzed. Respective failure criterions in principal stress space, principal strain space and octahedronal space are proposed from the results of the tests. 6) Triaxial compressive experiments on strength and deformation of concrete after freeze-thaw cycling are made. The effect of stress radios, cycles of freeze-thaw cycling on the strength of concrete is summarized. The unified failure criterion in octahedronal space are proposed from the results of the tests.The work stated in item 4), 5), 6) fills the blanks of experiment researches on strength and deformation of concrete under biaxial proportional compression, biaxial tension-compression and triaxial compression after freeze-thaw cycling, and also fills the blanks of experiment researches on strength and deformation of concrete under b...