Theoretical Study on Uplift Calculation of Embedded Twelve Ground Screws of Transmission Angle Steel Tower
In order to solve the problem of ground screw connection under large load of transmission angle steel tower,an embedded twelve ground screw joint structure was proposed.Based on the plastic yield line theory of stiffness difference evolution,the influence of the position of ground screws and the stiffness difference between ground screws and tower foot plates was considered,and the theoretical formula of uneven internal force between embedded ground screws and external ground screws under uplift load was derived.Then,combined with 24 sets of refined numerical analysis,the influence of different ground screw diameters,ground screw spacings,and tower foot plate thicknesses on the differences in uplift forces of internal and external ground screws was studied,and the correction coefficient of stiffness difference was calibrated.Finally,the theoretical formula was verified by 72 sets of numerical experiments.The research results show that the embedded twelve ground screw structure can improve the uplift bearing capacity of the joint by 40%-50%compared with the traditional eight ground screw structure;when the internal ground screw is arranged on the orthogonal line of the external ground screw,the uneven distribution coefficient of internal force of the internal and external ground screws under the uplift load is about 1.1,and it does not change with the diameter of the ground screw and the thickness of the tower foot plate.When the internal screw is close to the external screw along the diagonal,the uneven distribution coefficient of the internal force of the internal screw will decrease,but when the thickness of the tower foot plate increases,the uneven distribution coefficient will increase.The calculation results based on the plastic yield line theory of stiffness difference evolution of the tower foot plate are compared with the numerical simulation results.The average value of the ratio of the theoretical uneven distribution coefficient to the numerical uneven distribution coefficient is 1.01,and the coefficient of variation is 0.03.
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