| Along with the enormous transmission line construction, especially in the construction of UHV transmission lines, the manufacture of transmission tower, which is the basis of the transmission line project, has been concerned by construction department.Transmission tower is very sensitive to wind load, which would easily generate significant dynamic response. At present, wind loads are taken into account in most engineering applications only as static load to calculate, without checking fatigue effects of wind vibration on structure. When it comes to the transmission tower, the welded structures are greatly affected by wind vibration fatigue, especially for those parts being pulled and bended-Meanwhile, in order to improve the performance of transmission tower, especially in the tower strength, service life and environment benefits, HSLA steel is more and more applied in the manufacture of transmission tower. There are two main problems for Q420 steel application in UHV transmission tower, one is that the transmission tower under the wind load repeatedly function is easy to fatigue failure and further lead to destruction of the transmission tower for its poor weldability and the weld effect after welding. The second one is that the lacking research on Q420 steel welded joint fatigue failure.The paper took transmission tower structure under wind vibration as research project and centered on how to improve fatigue strength of welded structures. The wind resist property of the tower was also studied in the paper.The main contents are as follows.(1) Through studying wind load theory, metal fatigue theory and fatigue damage theory, predict transmission tower life based on wind-induced fatigue theoretically, forecast the wind vibration fatigue life of UHV transmission tower.(2) A comparative study was made of the welding method and welding parameter for Q420 steel, Conduct fatigue experiment research about transmission tower with a typical welded joints to determine the fatigue performance, welding joint process was optimized in order to improve the fatigue strength of welded joints.(3) Studied the main factors that influenced the welding joint fatigue life of transmission tower, mainly on both refining weld grains, reducing weld defects, propose better weld process and weld alloying to purify the welding metal, refine the grain and decrease the ratio of the cracks in the welding metal.(4) To ensure the fatigue life of the transmission tower,achieve high-quality welding steel of Q420 steel, increase the redundancy of welding process, though adding rare earth elements to the weld in order to improve the fatigue performance of welded joint. According to the experimental results and electrode material analysis, welding materials was developed for fatigue performance of Q420 steel. |
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