Study On Mechanical Properties Of Semi-grouting Sleeve Connection Based On Construction Defects

Prefabricated buildings are the product of continuous upgrading of the construction industry.With the progress of society,the development is getting faster,and their advantages are becoming more obvious.Semi-grouting sleeve connection technology is one of the main connection methods of prefabricated buildings.The connection performance is very important for the safety of structures.This paper is one of the research contents of "Research on Mechanical Properties of Fabricated Concrete Structure Reinforced Full-grouting Sleeve Connection after Fire" of Anhui Natural Science Foundation Project(1908085ME173).In the manufacture,installation and field grouting of prefabricated components of prefabricated buildings,due to that the operation level of construction personnel is not high enough,the operation mode is not standardized and other factors,which results in defects such as steel bar offset,steel bar bending and insufficient fluidity of grouting materials.These defects have a certain impact on the mechanical properties of steel bar semi-grouting sleeve connectors,which are inconsistent with the specifications of our country.At present,scholars at home and abroad have not systematically studied the mechanical properties of semi-grouting sleeve connectors under construction defects.Therefore,this paper studies the mechanical properties of steel semi-grouting sleeve under the above three defects by means of experiments,theoretical analysis,numerical simulation and other research methods.The main contents include: 1.Some material performance tests were done for steel bars and grouting materials.2.Twenty-four specimens(1 group of standard specimens and 7groups of defective specimens)were designed,and the causes of defective specimens were analyzed.3.Twenty-four semi-grouting sleeve specimens were tested in uniaxial tension,and the failure mode,stress distribution,stress transfer process,bearing capacity and deformation performance of the specimens under the defects of steel bar offset,steel bar bending and insufficient fluidity of grouting material were analyzed.4.The phenomenon and performance of the specimen under different defects were analyzed and compared with the test through uniaxial tension by ANSYS.The results show that: 1.The failure mode of all specimens is tensile failure of steel bars,which is subdivided into wedge failure,strengthening stage failure of steel bars and necking failure of steel bars.2.The strain of the steel bar in the anchorage section gradually increases from the position near the threaded end to the anchorage end,and the strain of the longitudinal sleeve gradually decreases from the position near the threaded end to the anchorage end.The minimum strain of longitudinal sleeve is at the threaded end or the anchored end of steel bar.The strain of the circumferential sleeve is very small,which may be tensile or compressed.3.In the process of stress transfer in the anchoring section of steel bars,grouting material is used as a medium to realize stress transfer from anchorage section of steel bar→grouting material→sleeve through the bonding effect between steel bars and grouting material and between sleeve and grouting material.4.In the process of uniaxial tension of the semi-grouting sleeve,the offset of steel bars,bending of steel bars and insufficient fluidity of grouting materials will affect the stress transfer effect in the specimen,but the effect is not great.5.The ultimate bearing capacity of the offset group specimen is not much different from that of the standard group specimen,but its displacement is greater than that of the standard group specimen.6.The ultimate bearing capacity of bending group specimens(except WZ-60 mm specimens)is not much different from that of standard group,but lower than that of standard group specimens.With the increase of bending degree,the bearing capacity of bent steel specimens decreases,and there is no obvious yield stage.When the ultimate bearing capacity changes little,the displacement of bent steel bar specimens is related to the bending degree,and its displacement increases with the increase of bending degree.In the elastic stage,the displacement of bent specimens varies greatly,and the displacement of WZ-40mm>WZ-20 mm > the displacement of standard group.In the strengthening stage,the displacement of the bent specimen is very small.7.The fluidity of grouting material decreases with the increase of time.The ultimate bearing capacity of the grout fluidity group is not much different from that of the standard group,and the displacement of the grout fluidity group increases with the increase of time.8.The finite element software simulation analysis is compared with the test.The results show that: 1.The failure mode of the specimen and the stress transfer law between the steel bar and the sleeve are consistent with the test.2.The error between the simulated yield load and ultimate load and the test results is small,the error of ultimate load is within 5%,and the error of yield load is within 4%.The simulation results are consistent with the experimental results.3.The trend of load-displacement curves is basically the same,which proves that the finite element model in this paper is reliable.Based on the analysis of test data,finite element simulation and test comparison,this paper summarizes the mechanical properties of semi-grouting sleeve connection under construction defects,looks forward to the future research direction,and provides theoretical basis for the safety performance of prefabricated buildings.Figure [85] table [16] reference [58]...