Experimental Study On The Connection Performance Of Square And Round Steel Tube Sleeves

Grouting sleeves are one of the key components for the connection of prefabricated building reinforcements.This connection method is through two steel bars butt joints in the steel pipe sleeve,and then grouted in the sleeve to achieve the connection of the steel bars by grouting and anchoring.With the emphasis placed on assembly-based building technology by the National 13 th Five-Year Plan,there are many research topics for prefabricated buildings,and the connection between steel bars and steel bars is also one of the focuses of research.This article through three tests,a total of 72 test pieces,progressively studied the following aspects: 1.Comparison of the same conditions under the condition of circular steel and square steel pipe anchorage performance;2.From three factors: The wall thickness of the sleeve,the length of the anchorage of the steel bar and the size of the inner diameter of the sleeve were used to study the effect of the steel pipe sleeve on the anchorage performance of the steel bar.3.The springs in the square sleeve were added to increase the anchorage performance of the steel pipe sleeve to the steel bar.Through a lot of comparative analysis of the data obtained from the experiment,the following conclusions are obtained:(1)Under the premise that the two sleeves have the same effective inner diameter,the load-displacement curves generated by the two kinds of steel tube sleeves with the same kind of connecting steel bars are found by comparing the load-displacement curves of the two sleeve samples.Basically consistent,it shows that the anchorage performance of the two types of sleeves is basically the same.In addition,by analyzing the axial strain and hoop strain of some square sleeves,it is found that the axial strain of the sleeve is positive,symmetrically distributed along the axial direction of the sleeve from the middle to both sides,and gradually decreases;the hoop strain is Negative,along the axial direction of the sleeve,is symmetrically distributed from the middle to both sides,and gradually decreases,indicating that the tension force sustained by the sleeve gradually decreases from the middle to both ends.(2)Analyze three factors that affect the anchorage performance of the sleeve: the thickness of the sleeve wall,the length of the anchorage,and the size of the inner diameter of the sleeve.The following conclusions are drawn: The thickness of the sleeve has a certain influence on the anchorage performance of the steel tube sleeve.The axial pull force of the sleeve is mainly borne by the built-in reinforcing steel.The sleeve is mainly responsible for the radial and circumferential restraining force of the grout material,and also bears a part of the axial pull force.The anchorage length also affects the anchoring performance of the reinforcing steel,but The longer the better,the longer the anchoring length of the sleeve is,the easier the grouting is not dense,and the anchoring performance is reduced;the larger the inner diameter of the sleeve is,the worse the anchoring performance of the steel pipe is to the steel bar.Under the condition that the load is constant,the steel pipe The larger the inner diameter,the greater the distance from the steel bar to the wall of the sleeve,the grouting material is subjected to a large moment of reinforcement,the grouting material is shredded or crushed at the position of the sleeve wall;the inner diameter of the sleeve is too small,and the ribs in the sleeve are too small.The grouting material between the inner wall of the sleeve is too thin,the influence of stress concentration on the grouting material is also relatively large,and it is also easy to be crushed,which also reduces the anchoring performance of the sleeve to the steel bar.(3)A spring is added to the square steel tube sleeve,and compared with a sleeve sample that is not added with a spring.The result shows that the spring is added to the sleeve to improve the integrity and overall rigidity of the grouting material,thereby improving the grouting material.The anchoring performance of the steel bar,but the improvement effect is not obvious.