380 m Ultra Long Span Crossing Tower: Design, Fabrication, and Construction

As the most critical portion of the 500KV Zhenhai~Zhoushan transmission line project. The Xihoumen Crossing is also one of the largest transmission line crossing projects in the world. The crossing scheme is "Strain-Suspension-Suspension-Strain", and the crossing spans are 1016m-2656m-521m respectively for each span; the total crossing length is 4.193km. The height of two ultra-long span tubular crossing towers is 380m, which currently ranks as the tallest transmission crossing tower in the world, based on the weather conditions of the area, the towers were designed under the high wind and wind plus ice conditions. Concrete-Filled Steel Tubes (CFT) were used for the main legs below 260m, and tubular steel members were used for other components. The production process and key fabrication technics will be introduced, which include the fabrication of the large diameter steel tubes, large sized X joints and K-joints, stiffened ball-joints, and trial assembly. Construction is the most challenging portion for such a heavy and tall tower, construction methodology will be discussed to cover installation plans and lifting equipment, erection of tower legs and cross arms, and pouring concrete into tower legs.