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RE: IBC Sec. 1617.1
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- Subject: RE: IBC Sec. 1617.1
- From: "Eric Ober" <eober(--nospam--at)holbertapple.com>
- Date: Fri, 12 Sep 2003 14:28:07 -0400
If you read the NEHRP and accompanying Commentary (section 5.2.7 of 1997 provisions) the 0.2Sds is intended to account for vertical accelerations, as you have interpreted. There have been similar provisions in other codes as well (BOCA, etc.). -----Original Message----- From: Jason Kilgore [mailto:jkilgore(--nospam--at)leok.com] Sent: Friday, September 12, 2003 2:06 PM To: seaint(--nospam--at)seaint.org Subject: IBC Sec. 1617.1 I normally work with buildings with a seismic design category of A, B, or C, so I rarely use Equations 16-28 through 16-31. (rho = 1, I don't use section 1617.1.2, and 0.2*Sds = about 0.02). Now I've got a problem with an Sds of 68%, so the second term in those equations is much higher. It's obvious that the first term acts horizontaly (Qe). I've always worked on the assumption that the second term acts vertically. For example, take a drag strut with vertical and horiz. loads. Assume rho = 1.5. E = rho*Qe +/- 0.2*Sds*D E = 1.5*Qe +/- 0.136*D You would then plug this value of E into, for example, Eq. 16-5: F = 1.2*D + 1*E + 0.5*L + 0.2*S F = 1.2*D + 1.5*Qe + 0.136*D + 0.5*L + 0.2*S F = 1.336*D + 1.5*Qe + 0.5*L + 0.2*S In other words, the "D" value from equations 16-28 through 16-31 are added to the "D" in whichever final load equation you use. Recently it was pointed out to me that the D in those equations is actualy a horizontal force, and should be directly added to Qe to get a purely horizontal "E" force. In other words, part of the horizontal load in a member is from the seismic base shear, and part is caused directly by the dead weight (and supported dead weight) of the member itself. I think this person is wrong, but would like other expert opinions. Thanks, ---- Jason Kilgore Leigh & O'Kane, L.L.C. ******* ****** ******* ******** ******* ******* ******* *** * Read list FAQ at: http://www.seaint.org/list_FAQ.asp * * This email was sent to you via Structural Engineers * Association of Southern California (SEAOSC) server. To * subscribe (no fee) or UnSubscribe, please go to: * * http://www.seaint.org/sealist1.asp * * Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you * send to the list is public domain and may be re-posted * without your permission. Make sure you visit our web * site at: http://www.seaint.org ******* ****** ****** ****** ******* ****** ****** ********
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- IBC Sec. 1617.1
- From: Jason Kilgore
- IBC Sec. 1617.1
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