直流跨越杆塔选型与结构优化

DC Crossing Transmission Tower Type Selection and Structural Optimization

大跨越高塔是以风荷载为控制设计的高耸结构,风荷载引起的弯矩甚至起决定作用。角钢构件与钢管构件相比,其最主要的是风载体型系数比钢管大,这也是角钢塔耗钢量高的主要原因。所有规格的角钢杆件均要进行稳定强度折减验算,而对常用规格的钢管而言几乎无需进行稳定强度折减验算。钢管材料各向同性,不存在强轴、弱轴之说,加之钢管的回转半径、截面刚度比角钢大,稳定性能大大优于角钢。并且跨越塔钢管方案总体价格比角钢方案低。因此,在三沪直流大跨越工程中,选择了钢管塔结构,塔身腹杆采用刚性腹杆,在塔头与塔身连接处设置水平横隔面。

Because bending moment on the large crossing tower caused by wind load is dominant, large span tall towers are structures that use wind load as a control factor in designs. Compared to steel tubular components, the uppermost problem of angled steel components is larger wind load coefficient, which is the main reason of higher steel consumption of angled steel towers. Stable strength discount check must be performed on all specs of angled steels. However, it is not needed for regular steel tubes. Tubular steel is isotropic without strong or weak axes. In addition, the radius of gyration and cross sectional stiffness of tubular steel are larger than that of angled steels, resulting in better stability. Furthermore, large span tower using tubular steel has a lower overall cost than angled steel design. Therefore, the tower design of Three Gorges-Shanghai DC Transmission Project adopts tubular steel with rigid web members and horizontal diaphragm between tower head and body.