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Steel HP piles and the IBC
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- Subject: Steel HP piles and the IBC
- From: Rick Burch <rburch(--nospam--at)conterra.com>
- Date: Sun, 08 Jun 2003 21:12:26 -0400
I just noticed some strange things in the IBC regarding steel piles. In 1808.3.5, the width/thickness ratio of the flanges of piles in Seismic Design Category D and above is limited. It looks to me like there are mistakes in equation 18-11 (and 18-12 for steel pipe piles), but I don't see any mention of them in the IBC errata up through the sixth printing of March 12, 2003. 1. The first apparent mistake is that the width/thickness of flanges is limited to 52*square root of Fy, however I feel sure this should have said 52/(square root of Fy), the same limit as in the AISC Seismic Provisions. Then, strangely enough, the equation in SI units is 0.317*square root (E/Fy). In other words, the SI equation is not just converted to different units, it has a whole new variable (E) in it. Fy is in the denominator as it should be however. 2. The same problems exist in the 18-12 equation for steel pipe piles. 3. Here is the real kicker. Lets say that the equation is really meant to be 52/(square root of Fy) same as the AISC Seismic Provisions. For A36, which HP piles are made of, this gives a ratio of 8.67. If you use b/2tf, also as the AISC does, there is not a single HP section listed in the AISC manual that meets this criteria. Since the IBC uses the same width/thickness ratio limits as the AISC Seismic Provisions (that is, if you assume the IBC equations are just wrong), you would assume the applicable ratio is b/2tf, also the same as in the AISC. However, the IBC uses the term "unsupported flange to thickness ratio", so maybe you could justify using (b/2-k1)/tf, in which case a few of the HP sections do meet the criteria. Can anyone shed any light on this situation? Are these equations wrong, and has the IBC essentially eliminated the use of steel HP piles for Seismic Design Category D and above? Or is the use of (b/2-k1)/tf reasonable? Rick Burch Columbia, SC ******* ****** ******* ******** ******* ******* ******* *** * 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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