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FW: Redundancy Factor
[Subject Prev][Subject Next][Thread Prev][Thread Next]- To: "'seaint'" <seaint(--nospam--at)seaint.org>
- Subject: FW: Redundancy Factor
- From: "La Count, Curt" <Curt.LaCount(--nospam--at)Jacobs.com>
- Date: Wed, 9 Jun 1999 09:42:00 -0700
One minor correction to the rho calculation below. The shear assigned to a bay is divided by the story shear under consideration. The maximum shear assigned to a bay is .7*2*4 kips=5.6 kips. The story shear at the base is 46.2 kips and so r max =5.6/46.2=.12. Using the other numbers provided, rho is now -1.43 which still indicates that you have a very redundant building. Use rho=1. >From a cursory look at the facts, this seems to be a very unsual building. By the assignment of shears, it looks like a 4 bay by 3 bay building which assuming even bays in all directions yields about a 14 ft. bay spacing. Unusual, even for semiconductor work. Let me know if I'm in the ballpark. Curt La Count Jacobs Engineering Portland, OR ---------- From: Dan Connell To: seaint(--nospam--at)seaint.org Subject: Re: Redundancy Factor Date: Tuesday, June 08, 1999 10:00PM I am just finishing a course at UCI which included this subject so I'll tell you what I have learned: The rho factor is a penalty factor for a non redundant system. When calculating the rmax factor, you use two adjacent columns. 70% may only be used on interior columns only. So say that you have a 4 column frame with the exterior columns taking 2.1 k ea and the interior ones 4 k ea and the total story shear is 20.2 kips. r1 = (2.1+.7*4)/49 = 0.1 r2 = (.7*4+.7*4) = 0.11 rmax = 0.11 for this frame at this story you must find rmax for ea frame at ea story. note that only the bottom 2/3 of the building need to be considered. if rmax = .11 and Ab = 2312, rho = 2-(20/(rmax(Ab)^1/2)) = -1.78 tne negative number says that you have a redundant system and you should use rho = 1. let me know if this is correct, -Dan Connell >From: rlewis(--nospam--at)techteam.org (Richard Lewis) >Reply-To: seaint(--nospam--at)seaint.org >To: seaint(--nospam--at)seaint.org >Subject: Redundancy Factor >Date: 09 Jun 1999 01:45:38 GMT > >I would like to start a new thread on the Redundancy Factor, Rho, of the >1997 >UBC. > >I have a 2 story concrete framed building. Total base shear is 46.2 kips. >Worst case shear in a frame line is 12.2 kips, with 4 columns. Ground >floor >area is 2312 SF. Now for a multi bay frame I use 70% of 2 columns to >calculate Rho. I get > >ri=0.7*(12.2*(2/4)/46.3 = 0.092 (from paragraph in 1630.1) > >Rho = 2-20/(0.092*sqrt(2312)) = -2.5 (eq. 30-3) > >Now this Rho is less than 1.0 so Rho min = 1.0 (paragraph in 1630.1) > >My question is, did I do this right? Can I calculate a Rho value less than >zero?
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