This paper proposes a 3D finite element mechanical calculation model of tower-line coupling system. Based on the analysis of the displacement and stress distribution of the strain section that under wind and icing condition, the safety margin curve under definite ice thickness and wind speed condition is proposed. As a result of calculated and verified the weak tower and weak elements of the tower, the characteristic of the weak position distribution is obtained. A working transmission line which happening a tower collapse accident is the subject investigated. The application of the mechanical calculation results to analyze the optimizing scheme of the operational transmission line, the methods that replace the steel type of the tower weak elements and add a tower in weak position of the strain section are proposed. Both the comparison critical curve of the strain section and the comparison curve of the tower weak elements stress ratio demonstrate the validity of the improved corrective recommendations.%建立了塔-线耦合结构系统三维有限元力学计算模型。通过对覆冰输电线路耐张段位移及应力分布情况进行分析计算，提出了线路耐张段在一定风速与覆冰厚度条件下的临界失效曲线。经过多次计算并验证薄弱杆塔以及薄弱单元分布情况，得到了薄弱位置的分布特点和规律。以发生覆冰倒塔事故的实际线路为研究对象，并以力学分析计算结果为依据，提出了有针对性地更换杆塔最薄弱处钢材以及在耐张段内薄弱处增加一基杆塔的线路改进方案。通过结构优化前后线路耐张段薄弱单元应力比值以及临界失效曲线的对比分析，证明了所提出改进方案的正确性和有效性。
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