Calculation of equivalent wind load due to lateral wind resonance (vortex-induced resonance) in freestanding chimneys

Thread Content

Dear Haihao friends: I have been working on the design of self-supporting steel chimneys recently. During the calculations, it was determined according to the standards that a check for lateral wind resonance was necessary. However, when calculating the equivalent wind bending moment using the formulas, both the starting height H1 and the ending height H2 of the locked zone are extremely low, ranging from 10^-5 to 10^-7. As a result, the λ coefficient becomes zero, and the equivalent wind bending moment for lateral wind resonance is also zero. The diameter at the top of the chimney is 1.224 m; the diameter at 2/3 of the chimney’s height is also 1.224 m. The total height of the chimney is 35 m, with a natural vibration period of 0.8756 s. It has a roughness class of A, with a roughness coefficient of 0.12, and the basic wind pressure is 0.61 KN/m2. Based on these calculations, the critical wind speed Vcr is 6.99 m/s, while the wind speed at the top of the chimney is VH = 41.09 m/s. Has anyone encountered this situation?