Analysis Of K-joint And Transmission Tower Based On Bolt Slippage

In traditional transmission tower design,truss model or truss-girder model is often used to analyze the structure.In recent years,some scholars have found that there are a lot of bolt slippage in the transmission tower through experiments.Results show that bolt slippage has a great impact on the deformation of the tower,and the theory of slippage is proposed.However,previous studies just analyze the axial slippage,ignoring the possibility of rotational slippage in some joints.So this paper is to study the rotational slippage of joints in transmission tower,the main work accomplished and results obtained are summarized as follows:(1)Considering the effects of material nonlinearity,geometric nonlinearity and status-changing nonlinearity,finite element model corresponding to the K-joint experiment is established.The final calculation of deformation and M- results of the model are in good agreement with the experiment,so the fidelity of the finite element model is comfirmed.(2)Eighty finite element models are established to parametrize the mechanical performance of K-joint,study the initial stiffness,sliding load,rotation of slippage,ultimate rotation,ultimate bearing moment under the influence of main angle size,number of bolts,pitch of bolts,applied load on bolts and bolt strength.The changing rules are summarized in this paper.(3)The rotational slippage curve is studied theoretically.The curve is divided into two parts,the first one is based on three-parameter power model according to Kishi-Chen,the second one is to express the Clearance slippage,finally the formula of the K-joint moment-rotation curve with slippage is obtained.Then based on the calculation results of the previous 80 joints,the calculation formulas of important parameters in the curve are fitted;The above two formulas can be used to calculate the load-displacement curves of slippage in different joints,which can be used to analyze the transmission tower structure considering bolt slippage.(4)Three transmission tower model is established,model I:don’t consider any slippage,model II: based on model I,the axial slippage is considered,model III: the rotational slippage is considered.In the modeling,the Connectors are used to define the axial and rotational slippage behavior at the joints,and analyze the influence of these two types of slippage on the transmission tower deformation and the internal force of the main members under bending and torsion conditions.Results show: Under the bending condition,the axial slip increases the tower body deformation by about 20%,and the influence on the main members’ axial force and moment is about 6% and 40%,the influence of rotational slippage on the moment of main members is about 20%,but the deformation and axial force are hardly fluctuated by rotational slippage.Under torsion condition,the axial slip increases the deformation of tower body by 2 to 3 times,the impact on the axial force is about 4% to 10%,and the influence on the torque of main members reaches 3 to 5 times,The rotational slippage has little effect on the deformation of the tower body and the axial force of the main material,but the influence on the torque of the main members is about 1 times.