输电塔为典型风敏感结构, 提升强风作用下输电塔的抗风性能是确保电网安全运行的关键。预应力拉索具有安装便捷、不占空间等优势, 该文首先提出一种输电塔体内拉索加固技术, 通过理论分析验证了该技术的可行性, 并构建了输电塔体内拉索体系性能提升评估框架; 其次, 基于理论分析确定了输电塔体内拉索加固技术实施方案, 并分别建立了加固前后输电塔有限元模型; 再次, 开展了结构非线性稳定分析, 并通过杆件稳定状态循环判断算法确定了输电塔的破坏模式和极限风速, 进而确定了输电塔体内拉索体系的抗风性能提升效果; 最后, 以220 kV典型输电塔为研究对象, 应用该文所提框架评估强风作用下输电塔体内拉索技术的加固效果, 并研究了不同拉索预拉力和截面积对输电塔体内拉索体系极限风速的影响。研究结果表明: 该技术可有效降低强风作用下输电塔斜材的轴力响应; 输电塔的破坏模式由加固前的斜材失稳破坏转变为加固后的主材压弯破坏, 极限风速由35.05 m/s提升至40.36 m/s; 拉索预拉力和截面积的增大均会导致极限风速降低, 当拉索预拉力为5.0 kN, 截面积为100.0 mm²时, 抗风性能提升效果最优。该文研究结果可为输电塔抗风设计优化提供参考。

Objective: Transmission towers are highly sensitive to wind loading. Improving the wind resistance of transmission towers is important for ensuring grid reliability. Prestressed cables provide easy installation and minimal spatial intrusion. An internal cable reinforcement method was proposed to improve the tower. Four internal cables were installed at the main member of the tower to reduce horizontal wind loads. Methods: The applicability of the internal cable method was confirmed using theoretical analysis. A performance evaluation framework for transmission towers with internal cables was introduced. The framework determines the cable reinforcement scheme through theoretical analysis. Truss idealization, pinned-joint modeling, and small-deformation assumptions were adopted to investigate axial forces in main and diagonal members after cable reinforcement. The optimal reinforcement scheme was determined based on the comparative reduction in member axial forces arising from reinforcement. Nonlinear stability analysis was implemented on finite element models of transmission towers with and without internal cables. The member stability cycle criterion was performed to ascertain failure modes and critical wind speeds. Tower failure is regarded as either the buckling failure of a single member or the yielding of a main element below the cable installation location. Results: A 220 kV transmission tower was used as the case study. Using the framework, the reinforcement effect under extreme wind was explored. The results revealed that the axial-to-force ratio in the lower leg member improved considerably after internal cable installation, while the axial-to-force ratio in diagonal members reduced substantially under extreme wind loading. Local yielding in the lower leg member below the cable anchorage precipitated structural collapse. The failure mode changed from diagonal buckling to leg failure after reinforcing. The critical wind speed rose from 35.05 m/s to 40.36 m/s. The critical wind speed increased by 15.0%, which led to a 32.6% enhancement in horizontal load-bearing capacity. Then, the influence of cable prestress levels and cross-sectional areas were investigated. Under varying cable parameters, the critical wind speed of the tower increased by 13.0%-16.0%. Therefore, cable cross-sectional area and prestress exert only a minor effect on wind resistance performance. As cable prestress and cross-sectional area increased, the marginal gain in critical wind speed progressively diminished. Raising the cable cross-sectional area decreased its ultimate stress, with further area increases above 100.00 mm² producing only marginal changes. Conclusions: The framework can be used to design cable-reinforcement schemes for transmission towers and evaluate the wind resistance performance of the reinforced tower-cable system. Cable reinforcement reduces axial forces in diagonal members along the tower. It reduces axial forces in lower leg members but raises them in upper leg members. For towers prone to leg-member buckling, internal cables with small inclination angles intensify compressive stresses in loaded legs. Therefore, external cables with larger angles are recommended. In towers where diagonal buckling governs failure, internal cable reinforcement substantially increases critical load capacity. The failure mode shifts to local yielding of lower leg members, and the capacity gain relies on the wind speed at which these members yield. Raising cable prestress or cross-sectional area decreases the critical wind speed for transmission towers with internal cables. The optimal wind resistance enhancement is realized with a cable prestress of 5.0 kN and a cross-sectional area of 100.00 mm². The research results of this paper can provide a reference for the optimization of wind resistance design of transmission towers.