覆冰荷载作用下500kV输电杆塔结构破坏机理试验分析

Experimental Analysis on Failure Mechanism of 500kV Transmission Tower Under Ice Loading

为考察高压输电塔结构在极限覆冰工况下的破坏模式和倒塌机理,以冰灾中破坏的典型500kV输电塔为原型,设计了一组单、双塔段子结构,模拟覆冰下荷载,进行了静力加载试验,对结构受力过程、破坏形态和应变及变形的发展情况等做了分析。基于通用有限元程序ANSYS,采用壳单元建立了加载塔段结构的实体模型,对试验全过程进行了模拟并与试验结果进行了比较。试验和有限元分析结果表明,主材构件的屈曲是输电塔结构在覆冰荷载作用下的基本破坏特征,斜材内力相对较小,但交叉斜撑面外变形较大。研究表明过大的交叉斜撑面外变形会显著地弱化主材的侧向约束,导致其计算长度增大,屈曲模态呈现出明显的弯扭失稳形式,从而显著地降低其承载能力,因此约束交叉斜撑的面外变形是提高整体结构抗冰承载力的一个主要途径。

In order to study the failure pattern and collapse mechanism of transmission tower under ice loading,a one-panel and a two-panel tower subassemblages of a typical 500kV transmission tower which were severely damaged during the ice disasters were fabricated.Both of two subassemblages were tested under simulated ice loading statically.The mechanical behavior,failure pattern,strain and deformation of substructures were investigated.The FEM software ANSYS was employed to analyze the behavior of two subassemblages by using shell elements.The experimental results showed that buckling of main leg was the basic failure mode of the structures,although the strains of the diagonal braces were relatively small.The out-of-plane deformations in the joints of the diagonal braces of the structures were considerable,and would significantly weaken the lateral constraining for main member of the structure.The effective length of the main angles would be increased.Meanwhile,the instability modes would exhibit obvious torsional-flexural buckling.The corresponding load-carrying capacity would be decreased notably.It can be concluded that restraining the out-of-plane deformation of the cross-bracings is one of the effective methods to enhance the ice load-carrying capacity of transmission tower.