Study On Static And Fatigue Behaviors In Tension For Concrete Under Lateral Pressures

Concrete is one of the most importance engineering materials for modem building structures, it is main specialty that compressive capability is better than tensile one. Though the studies on concrete compression is much more than tension, and these test results are gained universal recognition in compression, studies on tension is not only fewer on static but also few on tensile fatigue under multilateral pressures.This paper bases on a part of the project of National Natural Science Foundation "Failure criterion of concrete under multiaxial variable-amplitude fatigue loading"(50078010) for study contents. The main study contents are static and const- and variable- amplitude fatigue in tension under no-, one- and two-lateral pressure respectively in the paper, at the same time, history studies on uniaxial static and fatigue in tension are summarized, so this paper systematically studies both static and fatigue behaviors in tension for concrete under multilateral pressures, and establish a foundation for relative studies and applications.Main study contents in the paper are as follows:1) This paper tests static axial tension for concrete under no-, one- and two-lateral pressure respectively, compares ultimate tensile strengths under different lateral pressures, and compares static strain when tensile stress is maximum (named peak strain) and ultimate fatigue strain (that is total fatigue strain), fatigue life and fatigue deformation modulus ratio are also compared under different lateral pressures;2) This paper summarizes main shape and specification of specimens used for axial tensile tests for concrete, and also summarizes quantitative and qualitative relations between compressive strength and tensile strength (including resistance to breaking and splitting tensile strength) by adopted difference specimens shapes for concrete tensile tests, the behaviors of uniaxial tensile fatigue and flexural tensile fatigue under three-point loading in the end;3) This paper tests constant-amplitude fatigue in tension for concrete under, one- and two-lateral pressure, founds fatigue equations, and draws stress-strain curves. The test makes clear that strains, deformation modulus ratios of concrete fatigue present three-stage curves which are transformed into linear ones by defined two mathematic changes ?t and etm, this linear relation can easily estimate the changing trends of fatigue strains and deformation modulus ratios and the number of cycles.4) This paper carries out variable-amplitude fatigue tests in tension for concrete under one- and two-lateral pressures, and takes deformation modulus ratio of concrete fatigue as damage variable. This damage model not only is simple in style, but also predicting result of concrete fatigue life is better.5) This paper founds a computation flow on how to search out the best fitting equation of concrete fatigue for the special question, and obtains the best fatigue equation by using it, at the same time, this paper adjusts singular values of test data by using of EM algorithm which can forecast concrete fatigue life under the stress levels having not been tested too.