Research On Reinforcement Technology Of Steel Bar Cut Off In Sleeve Of Prefabricated Concrete Structure

The prefabricated concrete structure refers to a building in which the components are prefabricated in the factory and transported to the site to be assembled.Prefabricated concrete structure has the advantages of saving materials and labor,energy saving,environmental protection,etc,which are the development trend of the construction industry.In prefabricated concrete structures,sleeve grouting connections are usually used to realize the connection between components.The components sometimes have deviations during the production process,which make it impossible to connect the sleeve and the steel reinforcement during the installation process.In order to ensure the construction progress,part of the offset steel reinforcement will be cut off so that the components can be installed successfully.There is no steel connection between the members at the part where the steel bar is cut off,which becomes a defective part,so it needs to be repaired.Taking advantages of the characteristics of ultra-high performance concrete(UHPC),such as good fluidity and rapid strength development,a connection method in which UHPC is wrapped after one-sided lap welding of steel reinforcements is designed to repair the truncated parts of the steel reinforcements in the sleeve.In this paper,a tensile test is carried out on the specimens connected by UHPC wrapped in single-sided lap welding of steel bars,and the connection performance of the specimens under the influence of different factors is analyzed.The main work and achievements of this paper include:(1)The connection performance of the wrapped concrete specimens after the single-sided lap welding of the steel bars was studied.19 specimens under different working conditions were designed.The effects of different single-sided lap welding length,thickness of the concrete cover,anchorage length of non-welded parts,concrete material and connection mode are considered respectively.Each working condition has 4parallel test pieces,a total of 76 test pieces;(2)Through the test,understand the development of the cracks of the specimen during the test.The cracks of the specimen made by UHPC appeared late,and the concrete of the specimen began to crack from the edge line.The failure mode of the specimen after the test can be divided into three Type: Rebar break outside the test piece;rebar break inside the test piece;concrete splits and falls,and the remaining rebar is broken under stress by the single-sided lap welding weld;(3)Obtain the load-displacement curve of the test pieces,analyze the ultimate load of the test piece,and understand the influence of different factors on the connection performance of the test pieces.For the steel bar with a diameter of 16 mm,the thickness of the concrete cover should be 35 mm,single-sided lap joint for every 1mm increase in welding length,the ultimate load will increase by about 1.06 k N;for every 1mm increase in the anchorage length of the non-welded part,the ultimate load will increase by about0.52 k N;(4)Put forward the recommended size of the UHPC test piece wrapped by the single-sided lap welding of the steel bar,and study the repair technology after the steel bar in the sleeve is cut off.