角钢输电铁塔横担角度风荷载系数取值研究

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

完成了10 m/s、15 m/s和20 m/s来流风速下的2个角钢输电铁塔横担模型风洞试验,得到了19个风向角下横担的风轴阻力系数,分析了横担角度风系数、横线向和顺线向风荷载分配系数,构造了角度风系数函数并通过非线性拟合分析确定了拟合参数。在假定阻力系数相同的前提下,分别计算了由风洞试验和规范确定的横担有效投影面积。将试验确定的横担角度风荷载计算参数与国内外规范值进行了对比分析,提出了横担阻力系数、角度风系数和荷载分配系数的取值建议。中国规范计算横担阻力系数时,其计算式中的角钢构件阻力系数(1.3)建议由单片桁架阻力系数代替;风向角为0°时的横线向风荷载和风向角为30°时的顺线向风荷载取值偏于保守。

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.