Experimental Study On Mechanical Properties Of GFRP Bolt After Freezing-thawing Cycles And Long-term Load Effects

GFRP is short for Glass Fiber Reinforced Polymer, which is gradually being used in the civil engineering field as a new composite material. With mechanical properties of light weight, high strength and corrosion-resistant, GFRP bolt is applied to the reinforcement of the Road Slope Engineering and Geotechnical Engineering. It can deal with the problems such as steel bolt corrosion and difficulties in construction more effectively. But as so far, the researches on freezing-thawing durability and bond behaviour after long-term load are relatively less. So in this paper, a series of experiments have been done to test the long-term mechanical properties of the GFRP bolt. The main work and achievements of this article are as follows:(1)This thesis summarizes the existing research results of GFRP bolt’s bond behaviour and durability. Bond behaviour includes test methods, bonding mechanism, influence factors of bond strength, the failure process and failure forms, and the paper also discussed the bond-slip constitutive relations. Endurance performance summarizes the creep properties of the GFRP rod, besides the performances of bolt body after the freezing-thawing actions. All of above aim at providing evidence for durability test;(2)After exerting the freezing-thawing cycles, researches on the tensile strength and elastic modulus of GFRP bolt have been carried out in tensile test. According to the result, the author tries to find the change law of the tensile strength and elastic modulus of GFRP bolt. Then the author did a brief analysis of the performance reasons for the changes and fit the performance variation curve with the polynomial function. The research data can demonstrate that GFRP bolt performs favourably on resisting freezing-thawing actions;(3) After exerting the freezing-thawing cycles, the tests have been done to measure the bond strength and slippage of GFRP bolt through the pull-out experiment on bond behavior between GFRP bolt and concrete. According to the result, the author tries to find the change law of the bond strength of GFRP bolt. Afterward, the author did a brief analysis of the performance reasons for the changes and fit the performance variation curve with the polynomial function. From the research data, the conclusion can be drawn that the bonding performances of GFRP bolt after freezing-thawing actions is favourable;(4)By means of setting various loading size and loading time on the concrete-GFRP bolt specimen in a long time, studies have been performed to focus on the bonding strength and slippage of GFRP bolt via the pull-out experiment on bond behaviors between GFRP bolt and concrete. From the research the author tries to find the change law of the bond strength of GFRP bolt. Then, fit the curve of the performance variation considering single factor (loading size or time) with the exponential function. The research data indicate that the bond behaviours of GFRP bolt degenerate unremarkable and GFRP bolt has a satisfactory performance under long-term load.