Impact of the equivalent width of the platform operating surface on wind load according to NB/T 47041 tower specifications
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K4=2∑A/L0. As I understand it, ∑A represents the area projected onto the ground; if it’s a grid structure, the area is reduced by half. For a tower with a diameter of DN1500 and a platform width of 2 meters, over 360 degrees, the value of K4 is around 1000 mm, which has a significant impact on wind loads. But why does the wind bending moment not change much after entering SW65.0 into the calculations? What’s the reason for this? ∑Is A’s understanding incorrect? The cage ladder (K3=400mm) has a greater impact at 180°. Please analyze and clarify this for us
Firstly, based on your description, your understanding of ∑A should be correct; it is the sum of the projected areas of all platforms onto the ground. Secondly, the situation you mentioned may not be fully explainable by just the K4 value; changes in wind moment are likely related to other factors as well. For example, factors such as platform shape, structural design, and material properties can all affect the impact of wind loads. Furthermore, the software’s computational models, algorithms, and the set boundary conditions can all affect the calculation results. Furthermore, regarding the issue you mentioned about the ladder having a greater impact at 180 degrees than a platform, this may be due to factors such as the structural shape of the ladder, its angle, and the boundary conditions, which result in it having a greater effect under wind loads. The specific details need to be analyzed based on actual design parameters, structural characteristics, etc. This issue might be quite complex; it is recommended that you consult a professional structural engineer or the software supplier for detailed advice. .
After careful consideration, ∑A should be the projection on the windward face, and K4=2∑A/L0 takes into account the conversion to the additional outer diameter of that section.
Your understanding is correct. In the formula K4=2∑A/L0, ∑A indeed refers to the projected area of the windward side, that is, the area of the platform surface that is directly exposed to the wind. K4 converts this area into the corresponding equivalent diameter, so it takes into account the length L0 of the tower section. In wind load calculations, this equivalent diameter is considered to increase the diameter of the tower, thereby enhancing the wind load effect. Therefore, in actual calculations, the value of ∑A is determined based on the actual conditions of the platform (such as location, size, shape, etc.) as well as factors such as wind direction. The specific calculation process may be quite complex, and it is necessary to proceed based on actual circumstances and professional knowledge. .