Industrial pre-fab steel buildings, lateral wind deflection

[N Andersen]

The canadian steel code S16-09 limits lateral deflection of steel industrial buildings under wind load to H/200.

Wondering if designers of pre-fab steel buildings use a more relaxed limit, and if so how it is justified.

 

[ishvaaag]

At least in Spain, they did, coming to as low as H/120. It always seemed quite crazy to me, but some customers may accustomed to nice creaks and rips and elements flying.

 

[mrlc]

The Danish national annex to the European steel construction codes recommend these values for steel columns (these are deflections due to single variable loads):

Steel frames without cranes: h/150
Columns in single-storey buildings: h/300
Columns in multiple-storey buildings: h/300 and he/500

Where 'h' is the height of the column and 'he' is the height of the entire building.



/mrlc, the metric system, Denmark

 

[rowingengineer]

The selected deflection depends heavily on the type of analysis used to estimate the deflections. A simple analysis without the supports modelled as semirigid or similar obviously you can get away with a lower deflection limit knowing you have these up your sleeve.

An expert is a man who has made all the mistakes which can be made in a very narrow field

 

[N Andersen]

Yes....although if the footings are designed assuming the column bases are pinned (i.e. no fixed moments on the footings), shouldn't the frame be modelled this way to get accurate results?

 

[demayeng]

nda22: if the footings are designed for pinned columns, you should design the frame for strength using pinned bases as you say.
However under normal 'serviceability' loads (when you care about deflection) it is likely that you will have some significant rotational restraint capacity under these lower loads.

 

[rowingengineer]

There are a few good articles about this around the place this is one:

http://www.steelbiz.org/Discovery/ResourcePreview.aspx?ID=mYA+ddIXuT1og3WNrFXJ9A==

An expert is a man who has made all the mistakes which can be made in a very narrow field

 

[Ron]

Check the Metal Building Manufacturer's Association (MBMA)...they have publications and a manual that gives the design criteria. Here is a link to their website..

http://www.mbma.com

Here is an FAQ from their website and their response to same....

[highlight]What are the limitations on allowable drift (sidesway) in metal buildings?[/highlight]


This topic is addressed in the AISC’s Steel Design Guide Series No. 3: Serviceability Design Considerations for Low-Rise Buildings, as well as in the 1996 MBMA Low Rise Building Systems Manual.



The limitations for drift vary, depending on the type of material attached to the framing and the tolerance for movement. For example, for metal panels attached to framing, the recommended maximum drift is between H/60 and H/100 where H is the building height. It is also recommended that the wind load used to compute the drift when checking against these allowable limits should be based on a 10 year recurrence interval, which is approximately equal to 75% of the normal 50 year design wind pressure. For other types of cladding, refer to the references cited for more discussion.

 

[a2mfk]

Make sure if you are working with a PEMB, and you are designing CMU walls that are either cladding or part of the structure, that you coordinate the drift with them. Your CMU wall will not likely accomodate the drift they normally design for because they use all light-gage framing and panels for the walls. I have been through this whole thing before on a project and its a discussion you want to have early in the process. You may find the support for your CMU wall was designed to drift several inches!!