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RE: ACI318-99 load combination question
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- Subject: RE: ACI318-99 load combination question
- From: "Lutz,James" <JLUTZ(--nospam--at)earthtech.com>
- Date: Wed, 23 Aug 2000 17:12:11 -0700
Equation 9-6 governs. U=1.05(D+T) is what you would get from equation 9-5 if there were no live load, which is an unconservative load factor. Equation 9-6 creates a lower bound of a 1.4 load factor for "T" effects. I think the fluid load needs to be considered for all load combination equations, not just the few that are mentioned in the commentary. For equations 9-2, 9.2.3, and 9-5, however, I think the 1.4F goes inside the parentheses to be multiplied by the .75 reduction factor when wind or seismic loads are involved. If you do have fluid loadings, don't forget seismic effects on the fluid, which are part of the E loads. -----Original Message----- From: Zachary Goswick [mailto:ZachG(--nospam--at)angusyoung.com] Sent: Wednesday, August 23, 2000 2:57 PM To: 'seaint(--nospam--at)seaint.org' Subject: ACI318-99 load combination question Does anybody know whether equation 9-6 "U=1.4(D+T)" or the commentary on the same section saying equation 9-6 is "U=1.05(D+T)" is correct? It appears to me that they are saying two different things, or am I not seeing this correctly? Also, I am looking at section 9.2.5 and reading that 1.4F should be added to ALL combinations that have live load in them. The commentary says use just two equations "U = 1.4D + 1.7L + 1.4F" and "U = 0.9D + 1.4F". This does not seem to me to be ALL of the combinations with live load in them. Wouldn't this be all of the combinations given in paragraphs 9.2.1 through 9.2.7. as follows? U = 1.4D + 1.7L + 1.4F - from equation 9-1 U = 0.75(1.4D + 1.7L + 1.7W) + 1.4F - from equation 9-2 U = 0.75(1.4D + 1.7L + 1.7(1.1E)) + 1.4F - from paragraph 9.2.3 U = 1.4D + 1.7L + 1.7H + 1.4F - from equation 9-4 U = 0.75(1.4D + 1.7T + 1.7L) + 1.4F - from equation 9-5 It appears as if the second equation given by the commentary would not even be included in what the actual code says. Am I reading this incorrectly? Can anybody shed some light on these issues? I can figure out what would be the worst cases, but I am just trying to clarify what the code actually says. Please help! Zachary Goswick zachg(--nospam--at)angusyoung.com ******* ****** ******* ******** ******* ******* ******* *** * 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) to the list, send email to * admin(--nospam--at)seaint.org and in the body of the message type * "join seaint" (no quotes). To Unsubscribe, send email * to admin(--nospam--at)seaint.org and in the body of the message * type "leave seaint" (no quotes). For questions, send * email 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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