Comparison of Building Natural Frequency to Wind

[Lion06]

I am doing a dynamic analysis of a small building and need to compare the natural frequency of the building to that of the wind. I am having a hard time finding any literature that gives guidance on this or some guidance as to what natural frequency of a building is acceptable to avoid resonance with wind.
Does anyone know of any reference they can point me to?

 

[CJJS]

I wouldn't think wind in general has a natural frequency unless you are looking at vortex shedding.

 

[Lion06]

Do you know if there is anything regarding gust frequencies, that seemed to be what he was looking for.

 

[Lion06]

I am finding some pretty good stuff on vortex shedding. Everything I am finding seems to only reference this for a cylinder. Does anyone know if this can be applied to rectangles (which buildings usually are) and if so is the d (diameter of the cylinder) just the width of the building perpendicular to the direction of the wind? Thanks.

 

[prsconsultant]

You may look at the article listed below. It talks about the impact of wind on natural frequency of the building.

http://www.bssaonline.org/cgi/content/full/96/1/237#FIG011

I am not sure what your concerns are for a small building. Typically for buildings where we think the wind behavior plays a significant role, a wind tunnel study is performed.

 

[slickdeals]

Gust effects on buildings are important only if your building is flexible (which according to ASCE 7, is a building that a period > 1 second).

However, if you really want to research it and analyze it per ASCE 7, you can calculate a G value for a flexible building and associated eccentricities for torsion based on a flexible building. It will be a pain in the a** and don't know if it would be worth it on a small building.

 

[Lion06]

I think the vortex shedding frequency will be sufficient. I am not sure why this needs to be done for a 1 story building, as others have pointed out. Unfortunately, that isn't my call to make at this point. Does anyone know where to find strouhal numbers for different shapes?

 

[vincentpa]

what is the aspect ratio of the building h/L or h/B? If it is less than 4, ASCE 7 says you don't have to worry about it. In the commentary for ASCE 7, they give many natural frequecy ranges for various countries throughout the world. They all differ radically. So, maybe everyone in your office can put their guess as to what the natural frequecy of a building actually is and you can pick it out of a hat. The answer you get will be as good as anything you can calculate, which is worthless.

 

[Lion06]

I did just find that in the commentary. It also says if the natural frequency is greater than 1 you needn't consider it. It is a one story building and the H/least dimension <4 restriction is ok.