Influence of Refined Wind Load Parameters and Wind-Loading Mode on Wind-Induced Responses of a Long Cross-Arm Angle-Steel Transmission Tower

This study aims to investigate refined wind load parameters on main rods and the influence of wind-loading mode on wind-induced responses of the angle-steel transmission tower. The wind load parameters discussed in this study include drag coefficients, wind load distribution factors and skewed wind load factors. To achieve the aim, wind tunnel tests were conducted to explore aerodynamic loads for integrated frame, single frame, and main rod models of cross-arm and tower body. The wind load parameters of the different models were investigated. In addition, a series of wind-induced vibration simulation was applied to examine the wind-induced responses of an ultra-high voltage (UHV) transmission tower with a long cross-arm under concentrated and distributed wind loads. The simulated results under the two types of wind loads were compared. The results show that the longitudinal drag coefficients of the main rods are smaller than the values of the integrated frame, and equivalent on average to the values of the single frame. The experimental shielding factor of the cross-arm is larger than those in different standards due to the joint drag effects of leeward, upper, and lower faces of the cross-arm in the wind tunnel test. The experimented shielding factor of the tower body is in line with those referring to the Chinese and AS/NZS standards, and slightly larger than those based on the British and JEC standards. The skewed wind load factors of the main rod models are quite different from other models for cross-arm and tower body. The wind-induced vibration simulation suggests that, the wind-loading mode has limited impact on the displacements, accelerations, and gust factors of the transmission tower, but significantly influences the maximum normal stresses (MNSs) of the rods’ cross-sections. The MNSs caused by the distributed wind loads are obviously greater than those caused by concentrated wind loads, especially for the rods at the two ends of the cross-arm.