The maximum allowed drift for your building should also take into account
the siding/wall panels, connection details, supporting members, etc...
h/400 sounds pretty stiff unless you have some wall covering that is
susceptible to undesirable cracking. However, L/400 might well be resonable
for the supporting members (girt, spandrel, channel, etc.).
More flexible wall panels can withstand more drift without detrimental
effects. Pinned base details (at cmu/masonry/tilt-up wall bottoms) also
allow more drift. Tilt-up wall panels will typically have a pin base
detail, whereas a cast in place wall extending from a retaining wall will
have a more rigid/fixed base detail.
As Mark had stated, the drift is primarily a serviceability criteria and as
such most building codes to date have not set specific limits (for most
codes... not all). A good reference for acceptable drift is AISC Design
Guide #3 - Serviceability Design Considerations for Low-Rise Buildings.
Another reprint of this is in Appendix A15 of the 1996 Low-Rise Building
Systems Manual (MBMA )
As far as building codes, the City of Chicago has their own code. Outlying
areas around Chicago would most likely be BOCA or UBC (not sure which).
>From looking at BuildingTeam.Com it looks as though Cook County has their
own building code also. Not familiar enough with that code, if you don't
know the required code or have the specific code then you probably should
get a reply from an Illinois PE/SE (or building official) regarding the
building code from the area.
Hope this helps,
Greg Effland, P.E.
From: Jones, Mark A (Battle Creek) [mailto:Mark.A.Jones(--nospam--at)jacobs.com]
Sent: Wednesday, March 14, 2001 9:35 PM
Subject: RE: Wind drift requirement
Normally, I would direct you to the building codes, specifically the general
ones, where you would look in section 16 (usually) and the applicable
material code (e.g. ACI318 for concrete) . Your school should have a copy
of the applicable ones for the Chicago area. However, in this case, you
won't find it there. I know because I've looked MANY times. The long
standing rule of thumb is h/400. This is primarily based on serviceability
requirements, such as not popping off siding and keeping windows plumb.
From: tlee4 [mailto:tlee4(--nospam--at)uic.edu]
Hi, I was wondering if anyone could help a my group out by providing some
answers. We our designing and analyzing a 1-story frame arch building. It
would be built in the Chicago land area. We are having trouble determine
maximum drift and deflection for our building. So if anyone could help us
with the criteria for it we would appreciate it. Thank you,