Bearing Capacity Evaluation Analysis And Reinforce Of Transmission Tower Based On Tower-line System

Finite element model, simulating a500kV transmission tower-line system inmountainous area, has been established as groundwork based on theoretical analysisand prototype model tests. Icing bearing capacity and its reinforce toward thevulnerable spot of this model have been analyzed, so as the wind-induced vibrationand its control. Bolt-joint slip has been taken into account at the same time.The verifications of the static and dynamic behavious of the transmission linemodel betray that the error of transmission line shape-finding can be avoided by usingthe Initial Strain Adjusting Iterative Method (ISAIM), from which the model withhigh similarity both in static and dynamic can be established. On the other hand, Theverifications of tower models show that3Ds rigid-framed structure, concerning minusdeviation, geometrical non-linearity and material nonlinearity, has precise similaritywith actual towers.Icing bearing analysis of the transmission tower-line system indicates that theunbalanced tensile forces are main cause of the icing failure of the towers, and theultimate ice thickness of the transmission line is32.5mm locating the main angle ofthe upper corss arm of the tower No.81, a cathead tower, while the icing bearingcapacity of cupshape towers are greater than that of cathead ones. According to thevulnerable spot of the cathead towers, by means of adding another angle on theoriginal one forming a new member section “T” shape, the ultimate ice thickness canbe increased to35mm, by7.69%. Analogously, it can be increased separately to47.5mm and52.3mm, separately by46.15%and60.92%via the2ndand3rdreinforce,ideal effect gain. The bearing capability of wind load can be improved by111.46%atthe same time.The wind-induced dynamic responses of tower-line system have been analyzedbased on the wind load time-history simulation. The results show that the vibrationeffect is obvious that the average displacement on the tip of the tower No.81is about0.4m, while the dynamic displacement waves between0.28m to0.56m caused byfluctuating wind. The adjustment coefficients are calculated that the values of towerhead whitch is obvious to tower-line coupling are greater than that of tower body.Viscoelastic Dampers (VEDs) are used to control the fluctuating-wind-inducedvibration, and the maximum result is about40%so that the wind-induced vibration of the transmission tower-line system can be controlled effectively.Research on the influence of bolt-joint slip on icing bearing behavior andwind-induced vibration response of tower-line system based on the establishment ofstress-strain constitutive relation by means of Virtual Material Method (VMM)indicates that the displacement caused by the unbalanced tensile forces increases byabout10mm, while the slip have few effect on stress and the unbalanced tensile forcesthemselves. Simultaneously, wind-induced dynamic responses analyzing shows thatbolt-joints slip decrease the displacement by about30%to40%, while increase thelow amplitude acceleration result from the decline of the stiffness.