Research On Bonding And Lap Performance Of HFRB600 Steel Bar And High Strength Concrete

HFRB600 high-strength steel bar has higher strength and better ductility.The domestic research on HFRB600 steel bars is still in its infancy,and the relevant specifications in Henan Province have not yet been formulated.Therefore,in this paper,the influence of the concrete strength,relative protective layer thickness and anchor length on anchoring performance and overlap performance of the HFRB600 highstrength steel bars used in concrete was studied by the method of pull-out test.This work will provide a reference for the promotion of the application of HFRB600 highstrength steel bars in actual engineering and the compilation of related specifications.The main research work of this paper is as follows:(1)The pull-out tests were performed on 39 anchoring specimens of HFRB600 high strength steel bars and high-strength.The results showed that the bond failure was divided into: steel bar pull-out failure,concrete split failure and steel bar yield failure according to the difference in relative protective layer thickness and bond anchoring length.,and the characteristic and law of typical bond-slip curve under different failure modes were also studied.In which,The ultimate bond stress of HFRB600 high strength steel bars and high-strength concrete increases with the increase of the relative thickness of the protective layer and decreases with the increase of the bond anchor length.(2)The concrete split failure is the main failure mode in this paper.Therefore,for the split failure specimen,the calculation formula of the ultimate split bond strength of HFRB600 high-strength steel bars and high-strength concrete was proposed.Then,the bond-slip relationship curve model of HFRB600 high-strength steel bars and highstrength concrete for the split failure was built.(3)Through reliability analysis(center point method),the critical relative protective layer thickness of HFRB600 high strength steel bar and high strength concrete was determined.And verified that the current code "concrete structure design code"(GB500010-2010)is still applicable to the relative protective layer thickness.(4)The pull-out test of 9 overlap specimens of HFRB600 high strength steel bars and high-strength concrete were carried out.The test results show that all the specimens were subjected to yield failure,and the lapping length of 20 d has met the lapping length requirements of HFRB600 high strength steel bar and high strength concrete.And verified that the current code "concrete structure design code"(GB500010-2010)is still applicable to the relative protective layer thickness.