STUDY ON SKEWED WIND LOAD FACTOR ON CROSS-ARMS OF ANGLE STEEL TRANSMISSION TOWERS UNDER SKEWED WIND

Wind tunnel tests on two cross-arm models of an angle steel transmission tower under wind speeds of 10 m/s, 15 m/s and 20 m/s were conducted. The drag coefficients in wind axes for 19 skewed angles were obtained. The skewed wind load factors, the wind load distribution factors in the transversal and longitudinal directions were calculated. A fitting function for the skewed wind load factors of cross-arms was proposed. Two fitting parameters were determined by the nonlinear fitting analysis. With the assumption that the drag coefficients are in equivalent values, the effective projected areas (EPA) of the cross-arms were calculated. The parameters for calculating the skewed wind loads from wind tunnel tests were compared with standards both home and abroad. Suggestions on the drag coefficients, the skewed wind load factors and the wind load distribution factors were proposed. For the national standard, the drag coefficient of the angle steel members (1.3) should be substituted by that of the single frame in calculating the global drag coefficient of cross-arms. The transversal wind load for 0° wind incident angle and the longitudinal wind load for 30° wind incident angle are conservative.