Mechanical Properties Analysis Of New Type Prefabricated Inner Sleeve Connection Between Square Steel Tube Column And H Beam

Prefabricated steel structure buildings have many advantages such as superior seismic performance,short production cycle,flexible construction space,comprehensive economic benefits,and high comfort.The research and application in China is increasing.Steel structures are often prefabricated by beam-column connections.For the steel frame of the square steel tubular column and the H steel beam,since the square steel tubular column is a closed section,the high-strength bolt is difficult to be fastened,and the assembly process is difficult to realize.The sleeve is an effective means to solve the prefabricated connection of the closed section column,and it is also a research direction of the prefabricated connection of the square steel tube column H steel beam in recent years.In view of the existing problems of the existing steel tubular column prefabricated connection connections,this paper proposes a new type of assembled square steel tubular column H steel beam inner sleeve connection node form.Through the low-cycle reciprocating cyclic loading finite element calculation analysis,different structural improvement schemes are given.Through the comparative analysis of finite element results,an optimal node form is preferred.The ANSYS finite element software is used to establish the finite element models of the new sleeve assembly connections of the square steel tube column H steel beam.The finite element analysis of the static and low cycle reciprocating cyclic loads is carried out.By changing the thickness of the inner sleeve,the length of the inner sleeve,the thickness of the extended end plate,the arrangement of the pull bolt,the diameter of the pull bolt and the high-strength bolt,and whether or not the stiffener is set,the effects of various structural parameters on the mechanical properties of the connection were studied.Analyze the failure mode of the connection under low-cycle reciprocating cyclic loading,and study the performance of the connection's equivalent stress development,failure mode,hysteretic behavior and energy dissipation capacity,skeleton curve and bearing capacity,and node stiffness degradation.Analyze the seismic and ductile properties of the nodes.Research indicates:The new square steel tubular column H steel beam inner sleeve assembly connection node moves the splicing position of the upper and lower columns up to the beam-column connection,which not only provides installation space for the high-strength bolts of the beam-column connections,but also ensures the continuity of the connection node domain and achieves reliable force transmission.After the upper column is in place,the upper and lower columns are spliced by the pull bolts,and the upper end plate provides reinforcement for the column splicing.For the side connection,the reinforcing plate is added to the outer column wall to strengthen the connection of the upper and lower columns.The node is highly prefabricated.Under the static load,the increase of the thickness of the inner sleeve can reduce the stress of the column wall and increase the initial stiffness of the connection.However,when the thickness of the inner sleeve is too thick,the effect of increasing the initial stiffness of the connection is reduced.The thickness is appropriately increased;Increasing the length of the inner sleeve will increase the stress level of the column wall when the connection is broken,and reduce the initial rotational rigidity of the connection.Therefore,the length of the inner sleeve should take a small value.Increasing the thickness of the end plate can increase the initial stiffness of the connection,but it will increase the bearing capacity degradation at the end of the connection.It is recommended that the thickness of the end plate be appropriately increased.Under the low-cycle reciprocating cyclic load,the inner sleeve assembly connection of the new square steel tube column H steel beam shows good hysteresis performance,and the hysteresis curve of the connection is full of "spindle shape",indicating that the energy consumption of the connection is better.The node can finally realize the plastic hinge external displacement of the beam end,and the ductility coefficient is more than 3,which has better seismic performance and ductility;Increasing the thickness of the inner sleeve,the ultimate load,stiffness,ductility and energy consumption of the connection are improved.When the thickness is too large,the mechanical properties are not improved obviously,and the stiffness degradation after the yielding of the connection is accelerated.The strength of the integrated structure and the economic selection of the material are reasonable.It is recommended that the thickness of the inner sleeve is larger than the thickness of the column wall by 2 mm;Increasing the length of the inner sleeve,as the distance between the bolts and the column is farther away,the influence of the synergy of each component is reduced,the initial stiffness,ductility and energy consumption of the connection are significantly reduced,and the stress on the wall of the corresponding bolt is higher in the failure stage.Therefore,under the premise of meeting the structural requirements,it is recommended that the inner sleeve should not be too long;As the thickness of the end plate increasing,the energy consumption,ductility and connection stiffness of the connection will be changed.The thickness of the end plate is preferably greater than 2 mm of the thickness of the column wall;The increase of the diameter of the pull bolt has an adverse effect on the energy consumption capacity and ductility of the connection.Therefore,under the condition of meeting the force requirement,the diameter of the pull bolt should not be too large;The increase of high-strength bolt diameter has no significant effect on the stress distribution and hysteresis curve of the connection failure,but the ductility of the connection will be reduced.It is recommended that the high-strength bolt should take a smaller diameter under the condition of meeting the force requirement;The stiffeners can be used to significantly increase the stiffness and ductility of the joints.The stiffeners should be placed at the ends of the beams to improve the mechanical properties of the connection.Through the finite element analysis of the mechanical properties of the new square steel tubular column H steel beam inner sleeve assembly connection static and low cycle reciprocating cyclic load,the general mechanical properties of the new fabricated connection are obtained,and the different structural parameters are obtained.The comparative analysis of the change nodes gives some structural design suggestions,which provides a certain research basis for the promotion and application of the new nodes.