Experimental Study On Fatigue Performance Of SFPSC Under Hot-Wet Environment

In the bridge project, despite the use of common high-strength concrete can increase the strength of the structure, the brittleness problem which inevitably leads to is more serious. To solve the problem requires starting from the material itself, so that the material can have a high strength and enough crack resistance and durability. To this end, relying on a long-span prestressed concrete rigid frame bridge in Guangdong province which is under construction, the research group author in secondly developed the independent property rights ―Steel Fiber Reinforced Polymer Modified Concrete‖, and found a material named ―Steel Fiber Polymer Structural Concrete(SFPSC)‖ which can applied on the bridge superstructure, then studied the fatigue performance and durability of this material which under hot-wet environment. The main contents and conclusions are as follows:1) Researching and developing of ―Steel Fiber Polymer Structural Concrete(SFPSC)‖. According to the design requirements of the project(a grand prestressed concrete rigid frame bridge box girder) which the study relied on, the study is to R & D a new material whose compressive strength is similar to C55 concrete compressive, but with better toughness, crack resistance and durability. By the selection of raw materials, mix design and the basic mechanical properties and microscopic analysis of the new mixing material, the study has invented SFPSC which can meet all above requirements, and successfully applied to support project.2) Experimental study on fatigue performance of SFPSC under hot-wet environment. According to extreme service environment of the support project- high temperature and high humidity, using intelligent environment simulation and control system which developed by research group, as well as improved MTS810 test system, the study does the three-point bending fatigue tests under environmental and fatigue load coupling in high temperature and high humidity(50℃ and 95%RH) and atmospheric conditions at room temperature(23℃ and 78%RH), then obtained the S~N curve.3) Discussed the fatigue performance of SFPSC specimen under different environmental effects and hot-wet environment-load coupling or uncoupling effects. With the basic fatigue theory and assumptions, study has proposed the fatigue life expression of SFPSC three-point bending beam under hot-wet environment-load coupling. Using this expression, the fatigue life and fatigue limit of SFPSC specimen under hot-wet environment can be easily and effectively predicted.4) SFPSC three-point bending beam deformation law under hot-wet environment was discussed, and a damage model by its mid-span deflection parameters was established, then fatigue life prediction formula which described by damage variable was proposed. The results showed that when the damage variable reaches 0.28, SFPSC specimen entered the instability failure stage. Using this damage model, we can predict the fatigue life just by implement short non-destructive fatigue test of SFPSC specimen.