Wind Tunnel Test Study on Crane Structure with Double-Flat-Arm Derrick for Long-Span Transmission Towers

The construction of long-span power transmission lines in China is booming. These transmission lines run through large distances with high-rise towers, and are facing severe challenges from harsh environments. For construction of long-span and ultra high-rise transmission towers, the crane structure with double-flat-arm derrick has become the most important lifting equipment. During the construction process, the crane operates has to face the complex and extreme wind environment. The crane structure with a large slenderness ratio is quite wind-sensitive. Wind tunnel tests were carried out for the double-flat-arm derrick for erecting the 385 m high tower crossing the Yangtze River in Jiangyin. High-frequency force-balance wind tunnel tests were conducted for different working positions of flat arms under various incoming wind angles. The obtained shape coefficients of the standard tower body segment exihibited a linear relation with the incoming wind angles. It was also found that the overall shape coefficients of the crane structure obtained by the code might be risky, and should be paid more attention to the wind resistance calculation of the derrick structure. A refined wind loading calculation formula was proposed based on the member assembly method.