Theoretical Study on Uplift Calculation of Embedded Twelve Ground Screws of Transmission Angle Steel Tower
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摘要:
为解决输电角钢塔大荷载作用下的地螺连接问题,提出一种内嵌式十二地螺节点结构. 基于刚度差异演化的塑性屈服线理论,考虑地螺位置、地螺与塔脚板刚度差异的影响,推导出上拔荷载作用下内嵌地螺与外地螺内力不均匀计算的理论公式;然后,结合24组精细化数值分析,研究不同地螺直径、地螺间距和塔脚板厚度对内、外地螺上拔内力差异的影响,并对其刚度差异修正系数进行标定;最后,通过72组数值试验验证理论公式的合理性. 研究结论表明:内嵌式十二地螺结构较传统八地螺结构可以提高节点上拔承载力约40%~50%;当内地螺布置在外地螺正交线上时,内、外地螺在上拔荷载作用下的内力不均匀分布系数约为1.1,且不随地螺直径和塔脚板厚度变化;当内地螺沿着对角线靠近外地螺时,内地螺内力的不均匀分布系数减小,但当塔脚板厚度增大时,不均匀分布系数会增大;考虑刚度差异演化的塔脚板塑性屈服线理论的计算结果与数值模拟结果相比,理论不均匀分布系数与数值不均匀分布系数比值的均值为1.01,变异系数为0.03.
Abstract: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 about 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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表 1 尺寸参数
Table 1. Dimension parameters
mm 地螺
模型S1 S2 S3 L t 12M64 180 185 180.0,202.5,220.0 150 45,55,65,75 12M72 200 205 200.0,225.0,250.0 170 45,55,65,75 表 2 规格及荷载
Table 2. Specifications and loads
地螺模型 主材规格 地螺承载力/
kN施加荷载/
kN应力比 12M64 2L250 × 28 9954.7 8500 0.85 12M72 2L280 × 35 12871.2 11000 0.85 表 3 12M64地螺内力对比分析(S3=180.0 mm)
Table 3. Comparative analysis of internal force of 12M64 ground screw (S3 = 180.0 mm)
地螺
编号t=45 mm t=55 mm t=65 mm t=75 mm N/kN ψo N/kN ψo N/kN ψo N/kN ψo 1 716 1.08 695 1.11 677 1.10 694 1.06 2 745 755 740 724 3 669 662 674 668 4 741 1.04 759 1.03 741 1.06 735 1.05 5 730 738 753 747 6 668 667 674 683 7 765 1.02 755 1.02 751 1.03 753 1.03 8 726 733 740 740 9 656 678 682 681 10 756 1.14 744 1.13 765 1.17 758 1.15 11 648 641 654 648 12 681 672 649 670 $\overline \psi $ 1.07 1.08 1.09 1.08 表 4 12M64地螺内力对比分析(S3=202.5 mm)
Table 4. Comparative analysis of internal force of 12M64 ground screw (S3 = 202.5 mm)
地螺
编号t=45 mm t=45 mm t=65 mm t=75 mm N/kN ψo N/kN ψo N/kN ψo N/kN ψo 1 727 1.00 720 0.96 694 1.01 684 1.03 2 708 685 698 709 3 694 702 691 686 4 790 0.91 798 0.91 782 0.97 767 1.00 5 677 675 704 722 6 698 694 672 681 7 791 0.87 791 0.90 775 0.92 752 0.99 8 653 674 690 717 9 703 699 720 699 10 678 0.98 697 1.02 709 1.04 717 1.05 11 690 681 695 682 12 690 682 671 684 $\overline \psi $ 0.94 0.95 0.98 1.02 表 5 12M64地螺内力对比分析(S3=220.0 mm)
Table 5. Comparative analysis of internal force of 12M64 ground screw (S3 = 220.0 mm)
地螺
编号t=45 mm t=55 mm t=65 mm t=75 mm N/kN ψo N/kN ψo N/kN ψo N/kN ψo 1 762 0.76 762 0.81 720 0.90 710 0.93 2 583 602 642 654 3 777 731 706 702 4 826 0.72 813 0.80 797 0.85 759 0.93 5 569 617 646 687 6 746 739 725 722 7 848 0.73 830 0.80 807 0.87 785 0.92 8 576 619 662 690 9 740 719 716 712 10 594 0.80 623 0.86 678 0.97 684 0.98 11 752 713 710 710 12 728 731 690 685 $\overline \psi $ 0.75 0.82 0.90 0.94 表 6 12M72地螺内力对比分析(S3=200.0 mm)
Table 6. Comparative analysis of internal force of 12M72 ground screw (S3 = 200.0 mm)
地螺
编号t=45 mm t=55 mm t=65 mm t=75 mm N/kN ψo N/kN ψo N/kN ψo N/kN ψo 1 903 1.15 877 1.17 873 1.17 875 1.15 2 1024 1010 1009 1002 3 877 857 854 860 4 960 1.05 975 1.05 952 1.06 948 1.06 5 947 959 960 957 6 849 847 858 864 7 923 1.01 907 1.07 912 1.07 915 1.08 8 937 953 965 970 9 876 874 890 878 10 964 1.07 972 1.10 979 1.12 989 1.13 11 855 882 877 863 12 903 889 874 881 $\overline \psi $ 1.09 1.10 1.10 1.11 表 7 12M72地螺内力对比分析(S3=225.0 mm)
Table 7. Comparative analysis of internal force of 12M72 ground screw (S3 = 225.0 mm)
地螺编号 t=65 mm t=75 mm t=65 mm t=75 mm N/kN ψo N/kN ψo N/kN ψo N/kN ψo 1 950 0.88 924 0.99 903 1.01 910 1.04 2 836 900 905 932 3 943 900 892 888 4 1004 0.86 975 0.95 956 0.99 959 1.02 5 837 892 906 934 6 954 904 882 881 7 981 0.87 966 0.97 949 0.96 956 0.98 8 834 905 890 908 9 935 905 910 900 10 846 0.90 911 1.00 990 1.09 946 1.06 11 925 903 912 887 12 951 914 904 899 $\overline \psi $ 0.88 0.98 1.01 1.02 表 8 12M72地螺内力对比分析(S3=250.0 mm)
Table 8. Comparative analysis of internal force of 12M72 ground screw (S3 = 250.0 mm)
地螺编号 t=45 mm t=55 mm t=65 mm t=75 mm N/kN ψo N/kN ψo N/kN ψo N/kN ψo 1 1026 0.68 996 0.77 950 0.87 943 0.92 2 692 755 823 855 3 1014 979 942 918 4 1105 0.60 1054 0.70 1038 0.82 1012 0.87 5 637 721 806 844 6 1034 996 926 919 7 1093 0.62 1057 0.72 999 0.85 985 0.91 8 669 726 828 868 9 1048 972 952 924 10 656 0.65 772 0.78 819 0.85 861 0.92 11 1010 984 970 937 12 1023 990 954 937 $\overline \psi $ 0.64 0.74 0.85 0.91 表 9 不均匀分布系数均值$\overline \psi $
Table 9. Mean value of uneven distribution coefficient $\overline \psi $
地螺模型 t/mm S3/S1 1.000 1.125 1.222 12M64 45 1.07 0.94 0.75 55 1.08 0.95 0.82 65 1.09 0.98 0.90 75 1.08 1.02 0.94 12M72 45 1.09 0.88 0.64 55 1.10 0.98 0.74 65 1.10 1.01 0.85 75 1.11 1.02 0.91 表 10 数值试验参数
Table 10. Numerical test parameters
地螺模型 S1/mm S2/mm S3/mm L/mm t/mm 模型组数/组 12M64 180.0 195.0≥3.0d 180.0,202.5,220.0 150 45,55,65,75 12 225.0≥3.5d 260.0≥4.0d 12M72 200.0 195.0≥3.0d 200.0,225.0,250.0 170 45,55,65,75 12 225.0≥3.5d 260.0≥4.0d 表 11 上拔力计算结果对比
Table 11. Comparison of calculation results of uplift force
地螺型式 $\psi $ 最不利地螺内力/T 内嵌式十二地螺 1.0~1.1 0.083~0.089 八地螺 1.0 0.125 -
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