Experimental Study On Bonding And Anchoring Proporties Of New Type Four-sided Rib CRB600H Steel Bar And Concrete

CRB600H cold rolled ribbed bars with improved elongation is a new type of highstrength,high-ductility,and environmentally-friendly cold-rolled ribbed steel developed in China in recent years.It has broad application prospects in the construction field.At present,the CRB600 H high-strength steel bars used in the project are mostly found in two-sided ribs.For the four-sided rib CRB600 H steel bars,there is a lack of relevant understanding and research,and they are neglected in the market.In order to understand the synergistic mechanism between a new type of four-sided rib CRB600 H steel bar which adopts the irregular arrangement of transverse ribs and concrete,this paper studies its bonding and anchoring proporties through pull-out tests.The bonding mechanism of the new type four-sided ribbed CRB600 H steel bars in ordinary concrete members and the influence of various anchoring conditions on the bonding and anchoring proporties are analyzed.Based on the test results,the basic bond stress-slip constitutive model is obtained,and the recommended value of the anchorage length of the new type four-sided rib CRB600 H steel bar are given through reliability analysis,in order to solve the anchoring design problem and provide a reference for practical engineering applications.The main work of this paper is as follows:（1）The material properties test of the new type four-sided rib CRB600 H steel bar raw material was carried out,and compared with the corresponding national standard two-sided rib and national standard four-sided rib CRB600 H steel bar,the material properties of the three were analyzed;（2）The pull-out test of 204 specimens was carried out,and the whole process of drawing and the force law of the anchoring interface were analyzed in combination with the form of destruction.Based on the test results,The influence of the concrete strength,steel bar diameter,anchorage length and protective layer thickness on the bonding and anchoring proporties of the new type four-sided ribbed CRB600 H steel bar in ordinary concrete is researched,and the bonding proporties of the national standard CRB600 H steel bar under the same conditions was compared.The research shows that the anchoring conditions have varying degrees of influence on the bonding proporties between the new type four-sided rib CRB600 H steel bar and concrete.The new type four-sided rib CRB600 H steel bar has relatively anchoring advantages under the conditions of larger diameter and higher concrete strength.（3）The experimental results are fitted and regression by mathematical statistics methods,and the empirical formulas for the bonding and anchoring characteristic values of the new four-sided rib CRB600 H steel bar related to each influencing factor are obtained,and the average bond stress-slip curve is simplified to a four-fold line model,and Established a basic bond stress-slip constitutive model;（4）On the basis of the pull-out test,the anchorage length of the new type foursided rib CRB600 H steel bar in ordinary concrete was calculated by the anchoring reliability analysis and the anchoring length recommended formula in the Chinese and American specifications,and the recommended values for design of anchorage length is given through comparative analysis,which provides theoretical basis and reference for the application and promotion of this kind of high-strength steel bar in engineering.