Research On Tensile And Pull-out Behavior Of 8.8-grade Spliced Anchor Bolts

The column base joint is the key joint of the structure,and the anchor bolt is the key component of the column base joint.The failure of the anchor bolt will cause the failure of the column base joint,and then lead to the safety problem of the whole structure.There is still a lack of research on the embedded anchor bolt of column base joint in our country.The regulations of standards and important design manuals for the embedded anchor bolt are inconsistent,so the engineering designers are at a loss as to what to do with the design of the embedded anchor bolt.In this study,8.8-grade spliced anchor bolts are studied to realize the "detachable modification" and "repairable" of the column foot joint,and to improve the ductility and seismic energy dissipation performance of the column foot joint.This paper intends to determine the length of connection between 8.8-grade bolts with different diameters and steel thread coupler through monotonic tensile tests,and then determine the length of steel thread coupler with different bolt diameters.In order to determine the repairability of 8.8-grade spliced anchor bolt,this paper intends to carry out repeated pull-out test on 8.8-grade spliced anchor bolt specimen embedded in C40 concrete without considering the influence of the edge distance,In order to determine the influence of edge distance and reinforcement on the pullout resistance of 8.8-grade spliced anchor bolt,the monotonic pullout test of 8.8 grade spliced anchor bolt with small edge distance is carried out.The main research contents and results are as follows:(1)The ultimate tensile bearing capacity of 8.8-grade spliced anchor bolt with different bolt diameter and different connection length,the ductility of steel thread sleeve and anchor bolt joint,the relationship between average extrusion stress,average shear stress,average bending stress and joint length of joint joints under ultimate tensile load are studied.The design size of steel thread sleeve and the suitable connection length between steel thread sleeve and 8.8-grade anchor bolt are determined.The results show that when the length of the anchor bolt and the steel thread sleeve is the diameter of the anchor bolt,the joint failure will not occur under the tensile load,and the joint has good ductility.(2)The requirements of anchor bolt material and the classification of pre-installed anchor bolt from domestic and foreign code and design manual areintroduced.The classification of pre-installed anchor bolt failure types under pull-out test in domestic and foreign literature,the influencing factors of anchor bolt pullout performance are summarized.The design and calculation methods of ultimate state of pull-out bearing capacity of embeded anchor bolt given in domestic and foreign literature are compared.The results show that there is still a lack of research on pre-installed anchor bolt in our country,and the provisions of domestic codes and design manuals on the design of embedded anchor bolt are in a chaotic state,while the research on embedded anchor bolt in foreign countries has been very systematic.(3)The pullout resistance of 8.8-grade spliced anchor bolt embedded in C40 plain concrete foundation is studied.in order to study the repairability of the spliced anchor bolt with different embeded depths,The repeated pull-out test is carried out for the spliced anchor bolt which is not affected by the edge distance and spacing distance.The test results show that the force-displacement curve obtained from the test results is in good agreement with the four-stage model of the pullout force-displacement curve of anchor bolt.For 8.8-grade spliced anchor bolt embedded in C40 plain concrete foundation,the embeded depth of 10 times anchor bolt diameter is enough to realize the "repairable" of column foot anchor bolt.The monotonic pull-out test of8.8-grade spliced anchor bolt affected by edge distance is carried out.The concrete foundation of grade 8.8 spliced anchor bolt affected by edge distance is divided into reinforcement and unreinforcement,in order to investigate the influence of reinforcement on the bearing capacity of anchor bolt.The test results show that when the edge distance of anchor bolt is doubled,the bearing capacity of anchor bolt is obviously increased,and the reinforcement along the full range of embedded depth of anchor bolt is more obvious than that of increasing the edge distance of anchor bolt.