| Over a few last years,reinforced concrete structure has been widely used,but hugeeconomic losses have been caused by the corrosion of steel.Therefore,FRP bars are applied gradually,which become the focus of research in the field of civil engineering at home and abroad.Good bond performance of FRP bar embedded in concrete is the base of the structure to use,and is one of the emphases of design and popularize for FRP structure.However,the bond stress between GFRP bar and concrete is not as good as the steel bar.How to improve the bond behavior becomes a hotspot problem.The research work and conclusions are as follows:Based on the existing researches and the models of ?-s curve,the paper adopts micromechanical methods to investigate properties between the GFRP bar and concrete.This paper presents an experimental program with 45 pull-out specimens,to study bond behavior of FRP bar,including failure modes,bond strength,?-s curve and analyzes the difference of diameter,outer surface,loading rate and the failure mode on the bond-slip curve.The experimental result shows that:the GFRP bar with the the glass fiber on the outer surface has the maximum bond stress;there is no difference on the bond stress between the loading rate 1mm/min to 5mm/min;there is a level line on the top of the ?-s curve of the splitting failure mode,then descending suddenly,but there isn't a level line on the pull-out?-s curve,and the descending line is slow;based on the test results,the ?-s curve of GFRP bar with the glass fiber on the outer surface and the bar with sand and no rib on the outer surface corresponds with the MBPE and the continuous model greatly,the GFRP bar with the highest rib corresponds with BPE model.Based on the analysis of experimental results,the new ?-s law of GFRP bar embedded in concrete was established in this paper with the same fracture energy,the maximum bond stress and the corresponding displacement of the stress.We calculate the ?-s curve with the new model and discuss the accuracy. |
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