The Mechanical Performances Experiment On Joint With Double Pretension Steels Of Prefabricated Concrete Columns

The main components of prefabricated concrete structures are prefabricated in factories,assembled and connected on site.Prefabricated building has the advantages of high degree of mechanization,high labor utilization,low energy consumption and high engineering quality,which can eliminate many disadvantages of site construction.With the rapid development of China's construction industry,problems such as labor shortage and serious environmental pollution are gradually exposed.Therefore,PC structure is of great significance to the development of China's construction industrialization,improving production efficiency and saving energy consumption.At present,the country is carrying out industrial adjustment and deepening environmental governance.Building industrialization is put forward under this background.Prefabricated concrete structure is also an important measure to realize green building and improve the environment.In view of the problems of design and construction of assembled concrete column connection joints,on the basis the previous research of the research group,six reinforced concrete columns were designed and fabricated according to different eccentricities of the loading.The joints of three specimens were connected by grout-filled coupling sleeves according to Technical Regulations for Assembled Concrete Structures(JGJ1-2014);the other three columns were connected by grout-filled coupling sleeves with double pretension steel plates.The test data such as bearing capacity,the longitudinal deformation and the stress change of the tested columns under axial loading were obtained.Based on the test data,the results showed that:the control section of concrete columns connected by grout-filled coupling sleeves with double pretension steel plates behaved in accordance with plain cross section assumption,it conforms to the assumption of flat section.Under the condition of eccentric compression,the joint of double pretension steel plates can improve the bearing capacity and yield load of precast concrete columns.When approaching failure,sleeve grouting combined with tension steel plate connection test column shows better ductility.In the process of loading,the cracks in the tension zone of the test column with sleeve grouting combined with tension steel plate connections develop slowly,which effectively improves the sectional stiffness of the assembled concrete column.With the increase of eccentricity,the yield load and ultimate load eigenvalue of the test column with sleeve grouting combined with tension steel plate connections increase significantly.Based on the experimental research,the numerical analysis of the test column is carried out by using the analysis software ABAQUS.The analysis results show that the calculated values are in good agreement with the measured ones,which indicates that the mechanical properties of the assembled concrete columns with such joints can be analyzed in depth by using the finite element analysis software.On the basis of the experimental research,19 specimen models with 5 different parameters were established using the finite element software ABAQUS,and the effects of load eccentricity,pretension of tension bolts,reinforcement ratio of longitudinal force of assembled concrete columns,thickness of steel plate and connection mode of joints on the bearing capacity of assembled concrete columns are studied.The results showed that:the yield load and ultimate load of model columns with two kinds of connection joints decrease nonlinearly with the increase of relative eccentricity;the tension of the tension side of double pretension steel plates increased with the increase of eccentricity.Increasing reinforcement ratio can effectively improve the bearing capacity of model columns;under eccentric load,with the increase of reinforcement ratio,increase range of the ultimate bearing capacity of test columns with sleeve grouting combined with tension steel plate joints is weaker than that of simulation columns with sleeve grouting joints.With the increase of bolt preloading force,the confinement of steel plate to concrete is increased,and the eccentric compressive bearing capacity of simulated columns of sleeve grouting combined with tension steel plate connections can be significantly increased.The research also shows that the thickness of steel sheet has no significant effect on the bearing capacity of columns due to the relative slip between steel sheet and concrete in the loading process.