Experimental Study On Environment Fatigue Behavior Of Steel Fiber Polymer Structural Concrete

Engineering practices show that using ordinary high strength concrete can improvestructural strength,but it will make the brittleness problem of the concrete more prominent.Inorder to improve the toughness and crack resistance of ordinary high strength concrete,as thebackground of a highway that under construction,this study starts with the mechanicalproperties of materials and conducts the secondary development of "steel fiber reinforcedpolymer modified concrete" with independent intellectual property rights to develop a newcomposite material named steel fiber polymer structural concrete(SFPSC) which can be usedin long-span bridges.Considering the hot-wet environment in South China and coastalareas,the durability of this new material was further discussed by the experiment ofenvironment fatigue properties of SFPSC.The research results have important scientificsignificance and engineering application value for enhance the structure durability oflong-span concrete bridges. The main studying contents and co nclusions are as follows:1) Researching and developing of “steel fiber polymer structural concrete(SFPSC)”.According to the actual needs of a highway under construction, modified concrete materialcalled SFPSC which has similar strength of the existing high strength concrete such as C55concrete and better properties of cracking resistance and fatigue resistance was developedthrough a lot of mix design, material composition analysis and basic mechanics experiments.2) The S~N curves of SFPSC after the pretreatment of different hot-wetenvironment(50℃and80%RH；50℃and90%RH；50℃and95%RH) were obtained by thethree-point bending fatigue tests.According to the classical theory of fatigue strength andassumptions, the environment fatigue life expression of SFPSC was derived. And the constantcoefficients in the expression were determined by environment fatigue testing data. Using theexpression proposed in this paper, the environment fatigue life and fatigue limit of SFPSC inworking conditions of hot-wet environment of subtropical hot-wet climates can be effectivelyand easily predicted.3)Based on the research of the load-deflection curves and the fatigue lives-deflectioncurves, the three-stage variation law of the deflections of SFPSC beams was discovered. Therelative deflection-relative cycle count curves of the testing beams were obtained by havingdimensionless disposal testing data. And the effects of stress level and pretreatment of hot-wetenvironment changes deflection curves were studied.4) The analysis method using mid-span deflection to describe the damage variable D was proposed, and the fatigue life prediction formula was deduced. The results show that thedeductive value of damage variable is0.26when the SFPSC beams failure. Using this valueand some non-destructive fatigue testing data, the fatigue lives of SFPSC beams can be easilypredicted.