Study On Mechanical Properties Of Connections Between Rectangular Tubular Columns And H-shaped Beams Using Single Direction Bolts

Steel structure system has been widely promoted because of its light weight,high strength,good seismic performance,beautiful building shape,short construction period,flexible functional space layout,green environmental protection and recyclable advantages.Rectangular steel tubular columns and H-shaped steel beams are often used in steel frame structures,and beam-column connections are very important,which directly affect the bearing capacity and seismic performance of the structure.The existing connections between rectangular steel tubular column and H-shaped beam are usually welded joints,which have high strength and stiffness,but are prone to brittle fracture under strong earthquake.The assembled bolted connections have better seismic performance,but the existing bolted connections have more complex structure and higher installation precision.As a new type of bolt,single direction high strength bolts can be effectively used in the assembled connections of rectangular steel tubular column and H-shaped beam.In this paper,the mechanical properties of the single direction high strength bolt(STUCH-BOM)and the connection between rectangular steel tubular columns and H-shaped beam extruded end-plate with single direction high strength bolts are studied by means of experimental study and finite element analysis.(1)Through the unidirectional static loading test of three T-stub connections with single direction high strength bolts(STUCK-BOM)and two T-stub connections with routine high strength bolts,the failure mode and ultimate tensile bearing capacity of single direction high strength bolt were studied,the difference of mechanical properties between single direction high strength bolt and routine high strength bolt was compared,the effects of flange plate size effect on the mechanical properties of single direction high strength bolt and T-stub connections were analyzed.Research shows that the failure mode of single direction high strength bolt and routine high strength bolt are different,and the failure of single direction high strength bolt is due to the pull out of the bolt,which caused by the extrusion bending deformation of its outer sleeve;The ultimate tensile bearing capacity of single direction high strength bolt and routine high strength bolt is basically the same;The tensile bearing capacity and initial stiffness of T-stub connections with single direction high strength bolts are basically the same as T-stub connections with routine high strength bolts.The capability of plastic deformation of T-stub connections with single direction high strength bolts is weaker than T-stub connections with routine high strength bolts.Bolt spacing and bolt edge distance has little influence on the ultimate tensile bearing capacity of single direction high strength bolt,and bolt spacing has little effect on the tensile bearing capacity of T-stub connections,and bolt edge distance has a certain influence on the tensile bearing capacity of T-stub connections.(2)In order to study the seismic behavior of connections between rectangular tubular columns and H-shaped beams using single direction bolts,the pseudo-static tests of five connections using single direction high strength bolts and one connection using routine high strength bolts were carried out.The failure modes,hysteretic curves,skeleton curves,ductility,energy dissipation and stiffness degradation of connections between rectangular tubular columns and H-shaped beams using single direction bolts were studied.The differences in seismic behavior of connections using single direction high strength bolts and routine high strength bolts were compared.The influence of structural parameters on the seismic behavior of connections using single direction high strength bolts was analyzed.According to the hysteretic characteristics of the connections and the stress characteristics of the single direction high strength bolts,the restoring force model of connections was put forward.The results show that:(1)The phenomenon of"slip"is produced by the single direction high strength bolts in all the failure modes of the connections.(2)The hysteresis curves of the connections are"pinch"seriously,the shape of the hysteresis curves is reverse"S"shape and the hysteresis curves produce obvious slip straight line.(3)The initial rotational stiffness of the connection is about 70%of that of the connection using routine high strength bolts.The slip of the single direction high strength bolts makes the connections have a great rotational deformation capacity,and the limit rotation angle of the connections is 0.06~0.08rad.(4)The bending capacity of the connections is basically the same as that of the routine high strength bolts,and the single direction high strength bolts can meet the design requirements of the connections.(5)The equivalent viscous damping coefficient of the connections is?_e=0.15~0.17,and the equivalent energy dissipation coefficient is E=1.29~1.77,and the ductility coefficient is?=1.81~2.26,and their energy dissipation capacity and ductility performance are both not as good as that of the connection with routine high strength bolts.(6)Setting the stiffener of endplate can effectively improve the seismic behavior of the connections,and the effect of setting up inner diaphragm on the seismic behavior of the connections is not obvious.(7)The calculation curve of the restoring force model is in good agreement with the experimental curve.(3)ABAQUS finite element analysis software is used to establish the finite element model of joint specimens.The finite element model of single direction high strength bolts is established by simplifying the complex structure and contact problems of single direction high strength bolts.The bending behavior of the connections between rectangular steel tubular columns and H-shaped steel beams with single direction high strength bolts under monotonic static loads is studied by finite element simulation.The results show that:(1)In the finite element simulation results of connections,the failure modes of single direction high strength bolts and connections,the bending capacity of connections and the initial rotational stiffness of connections are in good agreement with the test results,and the accuracy of the test and finite element simulation results is verified by cross validation.(2)The connection between rectangular steel tubular columns and H-shaped beam extruded end-plate with single direction high strength bolts shows semi-rigid characteristics,which is a typical semi-rigid connection.