Wind loads on a small structure?

[SteelPE]

I have a structure that is square in shape and relatively slender (12’ square by 70’ tall). I would like to capture the wind loads applied to the structure in each orthogonal and along an axis skewed 45 degrees to the structure. In my computer model I ended up making two separate structures one oriented along the orthogonal axis and the other where I rotated the structure 45 degrees.

When it came time to apply the loads to the skewed structure I used the same loads I had used along the orthogonal axis. I am now questioning if this was the correct approach as the wind load will never actually hit the broad side of the structure.

The possible error was brought to my attention as I was calculating the reactions at the base by hand and realized that my moment at the base was 41% higher along the skewed axis. I thought this was find until I broke out the loads into the footing orthogonal axis and realized I had the full wind applied in both directions at the same time which didn't seem correct to me.

Hopefully my picture will be able to better describe my question.

 

[Leftwow]

I like to look at it like an aluminum boat moving through water. The amount of water displaced below the surface plus the frictional force of surface tension between aluminum and water would be the controlling factor. I think that the curved flat bottom aluminum boats displace the same amount of water as the angled aluminum boats. Therefore, causing the same amount of force. Only reason they like curves is because the flat bottoms tend to bounce around, hence the only vector coming from the engine and prop itself.

 

[SAIL3]

If the OP is interested in a more in-depth knowledge of wind on open frame stuctures and how it is treated throughout the engineering community , there is an excellent book published by ASCE.."Wind Loads and Anchor Bolt Design for Petrochemical Facilities"..highly recomend it..it is clear , logical and practical...

 

[steellion]

The Citicorp building sits on stilts. Do a Google image search and the problem with designing the building for wind on the orthogonal faces only will be immediately apparent. My understanding is that there was no code requirement at the time to look at wind on the corners of the building, but as it was being built, Le Messurier recognized that the building would be not be safe against wind in that direction and designed modifications to fix it.