To: "Structural Engineering Forum (E-mail)" <seaint(--nospam--at)seaint.org>
Subject: RE: Drift
From: Bill Marczewski <bmarczewski(--nospam--at)martind.com>
Date: Wed, 27 Jun 2001 13:22:38 -0600
probably know, few codes or standards address drift limitations. I work in
seismic zone 1 (Denver, Colorado), and we therefore limit our building drift to
account for a desired building performance due to wind loading. For wind
drift on buildings we typically limit those values from 0.0015 to 0.0035
times the building/story height, and simultaneously limit seismic drift to a
value of about 10 times greater (0.015 to 0.035).
the case of your auto dealership, I concur with the previous response from
another, that the window manufacturer or architect can provide information on
how much movement the window can tolerate within the frame. We often
ask this question when designing office buildings to determine how much
beam deflection to allow. The typical response is that the window can move
about 1/2" within the window frame.
If you have a higher risk of an seismic event than we
do here in Denver, than I would suggest you consider designing your structure to
account for drift due to seismic forces with (0.0035)*(H) being your maximum
allowable displacement. In doing so, you should have covered drift
requirements for daily loadings such as wind/gusts, and still have a sound
structure after a seismic event.