Research On The Mechanical Behavior Of High Strength Bolted Joint With Vertical And Diagonal Bars And Parameter Analysis

Steel bridge's advantages that great span capability,suitable for industrial manufacture,convenient for transportation,fast installation and so on,make it develop quickly.And the splice joint contected by the friction type high strength bolt is widely used in steel structure bridge.But the problem that bolt breakage is widly existed in the high strength bolt joint of steel structure bridge.It is of great significance to analyze the performance of high strength bolted joints with vertical bars,diagonal bars and chords in order to ensure the normal use of this kind of bridge.In this thesis,the high strength bolted large joints' whole finite element model and local model are established using ANSYS software.The transmission ratio,stress distribution of core plate and splice plate,load-slip relationship and so on are analyzed.And the influence of the bolt missing,the thickness of the plate and the diameter of the bolt hole on the force transfer performance of the bolt group are analyzed.Specific research contents are given as follows:(1)The force transfer ratio of the bolt in the bolt group(including three columns)distributed along the longitudinal direction by the bridge piece type,in other words,the first row and the last row of bolts' force transfer ratio are relatively large,and the middle row bolt's is small.The shear force of the bolts in the bolt group containing six columns distributed along the plate into W type.The difference of the transmission ratio of each row of bolts will increases with the increase of the number of high strength bolts.However,the transfer ratio of the first row of bolts in the bolt group is almost unchanged,and the transfer ratio of the bolt in the middle is reduced.(2)The axial stress on the cross section of the core plate distributed by wavy spread,that is to say,the stress of bolt axial connection is small,and the stress between the lines is larger.The axial stress distribution along the longitudinal direction of the buttcover plate that between two rows of bolts is distributed by wavy spread,this means that the stress on the bolt center line is small,and the stress between the bolts is larger.Splice plate's stress between the two rows of the bolt transverse wavy distribution along the plate,instead,the stress along the bolt connected line is small,but the stress between the lines of the high strength bolts is larger.(3)The Shear strength passed by the high strength bolt's relationship with the external loads applied to the model take on direct proportion,but the shear value of each bolt is various.As long as there is a bolt sliding in the bolt group,and the Shear strength passed by the high strength bolt's relationship with the external loads applied to the model begins to show a nonlinear relationship,and the later high strength bolt appears slide,the nonlinear relationship between them is more obvious.After the higth strength bolts group entering the local slip stage,the shear value of each bolt on the same row is quite different,so it is necessary to take into account the the bolt force 's inhomogeneity along the width of the plate when analysis the force of the bolt group.(4)The heterogeneity of the shear force of each bolt in the bolt group increases with the increase of the thickness of the splice plate,that is to say,the transmission ratio of the first row bolt increases,the transmission ratio of the last row of bolts is reduced,and the middle row bolts' transmission ratio is barely change.With the increase of the thickness of splice plate,the earlier the bolt slipping occurs.The splice plate thickness has no influence on the ultimate slip load of the joint.(5)The pressure influence zone of high strength bolt increases with the increase of bolt diameter,and it's diameter is about 2.85 times the diameter of the bolt hole.With the increase of bolt diameter,the force transfer ratio of the first row of bolts is decreased,and the transmission ratio of the last row of bolts increases,and the middle row bolts' is barely change.The contact stress between the splice plate and the core plate decreases with the increase of bolt diameter.(6)In the large joints with vertical rods and inclined rods,the loss of the bolt is only affect the number of rows of bolts close to the center of the rod,and the influence is not obvious.In the local model,the loss of the bolt has an influence on the transfer ratio of the bolt within 2 times of the bolt distance.The loss of the bolt will lead to the decrease of the initial sliding load of the bolt group and the decrease of the ultimate slip load of it.The lack of bolt has little influence on the load-slip curve along adjacent bolt group.