Experimental Study On Bearing Capacity Of Steel Tube Sleeve Grouting Connection

At present,most of the civil buildings in our country adopt the cast-in-place concrete structure,the construction process is slow and the environmental pollution is serious.With the advantages of fast and convenient construction,prefabricated concrete structures are more and more used in practical projects.Different from the one-time pouring of joints in cast-in-situ structures,the beam and column joints of prefabricated structures need to be connected twice at the construction site,which poses a great challenge to the connection technology of components.The performance of compression and bending bearing capacity of the sleeve grouting connection used in the connection of concrete-filled steel tubular columns is tested and analyzed.The test is divided into unidirectional axial compression performance and unidirectional and cyclic load bending performance test.The outer diameter of the steel pipe is 168 mm,the outer diameter of the sleeve is 219 mm,and the thickness of the steel pipe and the sleeve is 8mm.The bending test specimens are divided into 4 groups according to different axial pressures and loading methods.The axial pressures of the test specimens are 0.2N₀ ? 0.6N₀?N₀ is the axial compression bearing capacity?.Based on the test results,the bearing capacity,failure mode,vertical displacement,sleeve strain,hysteretic curve and skeleton curve are analyzed.The test results show that when steel tube sleeve grouting connection is under compression and bending load,as the axial pressure increases from 0.2N₀ to 0.6N₀,its horizontal load bearing capacity decreases by 30%,and the yield displacement angle decreases from 2.5% to 1%.It becomes worse,but its stiffness is improved.Due to the effect of bending moment,the gap between steel pipe and grouting material near the two ends of the connection is more likely to occur,and it is also more likely to be crushed under the effect of contacting compressive stress.The sleeve here will be ovalized,which will cause the shear key to fail.Analyze the hoop strain of the sleeve.And after simplification,a calculation model for the bending load of the steel tube sleeve grouting connection can be obtained.The calculation model shows that the smaller the axial load,the more the connection tends to the bending failure mode.When the axial pressure is greater,when the connection is broken,and the axis tends to be damaged by compression.According to the calculation model of the bending capacity of the steel tube sleeve,the calculation formula of the ultimate bending capacity of the connection was derived on the basis of the strength under the triaxial compression-compression-tension state of the grout and the circumferential strain of the sleeve.Figure 62;Table 10;Reference 63.