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Re: Redundancy Factor

[Subject Prev][Subject Next][Thread Prev][Thread Next] 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) (Richard Lewis)
Reply-To: seaint(--nospam--at)
To: seaint(--nospam--at)
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

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

Richard Lewis, P.E.
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