Investigation on aerodynamic characteristics for steel tubular cross-arms of transmission tower under skew wind

Abstract

A study of the aerodynamic characteristics of steel tubular butterfly-shaped cross-arms in a transmission tower head under skew wind is presented. A wind tunnel test was conducted under skew wind by using a scaling model, and a numerical simulation was performed with a high-precision three-dimensional tower head model. The drag coefficient, skew wind load factor, and wind load distribution factor of the cross-arms obtained from the experiment and numerical simulation were identified and compared with those acquired from different codes. It is concluded that the indirect force measurement method was found to underestimate aerodynamic forces acting on windward cross-arms. For single cross-arm, the horizontal cross-arm showed stronger shielding effect than the inclined cross-arm. A fitting formula for the skew wind load factor of the cross-arm is proposed, and values obtained from it matched experimental and simulation data well. A comparison between calculated and measured wind load distribution factors showed that although longitudinal load distribution factors calculated with the Chinese standard (2018) were consistent with measured data, calculated transverse load distribution factors did not match measurements well. It is suggested that the effect of the transverse lift wind force should be considered in the calculation of wind load distribution factors.