Wind Drift Limits for High Rise Buildings

[ERIFW]

I am working through the preliminary design of a 13 story building (steel framed with X bracing) and was hoping to get some feedback on how others go about checking wind drift/interstory drift in their designs.
(1) Do you check the drift just at the center of rigidity?
(2) Do you check the drift at each frame?
(3) Do you check the drift at any point of the floor plate (even the far outside corners)?
(4) Do you check drift just using the main X and Y wind cases or also the torsional wind cases?

I feel like you should check the drift at any point on the floor plate for any wind case, including the torsional case, but am I stacking the deck again myself by doing this?

Any thoughts would be appreciated?

 

[haynewp]

Wind drift is usually a serviceability consideration. H/400 max is what I would start looking at under a serviceability wind (10 year return) of such a building under the worst case deflection of a floor considering all combinations and locations you mention, and use some judgement if there is a large difference. I think it used to be H/400 at the geometric center or center of rigidity before all the torsional cases came along.

 

[asixth]

H/500 interstorey drift for me using a 20yr wind (AU standards). And I make the check for the maximum diaphragm displacement.

 

[steellion]

H/400 at the center of rigidity and H/300 at any point on the floor slab at each story under 10-year wind.

 

[slickdeals]

@Steellion,
Is that your company's standard or is there documentation of this limit anywhere? Buildings these days are not symmetric and usually the twist component is a good chunk and when added to the sway component can cause the deflection at extremities to exceed H/400.

What are you suggesting seems to make sense. Would appreciate any references you have.

 

[steellion]

That is our company standard. I am not aware of any formal requirements or documentation for wind drift limits anywhere, just various articles published on the topic. I these numbers come from an amalgam of various articles and preferences of experienced engineers. They "feel" right to me.

 

[JAE]

Try the AISC Engineering Journal, First Quarter 1993.

They have a nifty table outlining all sorts of drifts based on exterior cladding and supporting frame.

This is not code required in the U.S. for wind.

Check out Eng-Tips Forum's Policies here:
faq731-376

 

[ERIFW]

Thanks for the thoughts/info.

One other topic I would like to hear what other's do...Do you typically model the foundation conditions as idealized pins or do you use estimated spring constants for the vertical and horizontal reactions? Probably has a little to do with the size of building and the program you are using. RAM only allows vertical springs whereas RISA allows for springs in any direction. On the 13 story building mentioned above my lateral deflections double when I swap out the idealized pins for springs.

Any thoughts would be appreciated.

Thanks.

 

[KootK]

Ignoring soil flexibility completely seems hopelessly optimistic to me. Some accounting should be given to it, even if it's extremely crude. Much depends on how your superstructure will interact with your basement levels if you have them.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[mike20793]

Definitely recommend the paper JAE is referring to. It's what I use for wind drift for varying types of cladding.