• To: "'seaint(--nospam--at)seaint.org'" <seaint(--nospam--at)seaint.org>
• Subject: ACI318-99 load combination question
• From: Zachary Goswick <ZachG(--nospam--at)angusyoung.com>
• Date: Wed, 23 Aug 2000 16:57:05 -0500

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