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Re: Maximum Moments in Beams

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Is the equipment supported at the top for lateral loads or is the equipment considered fixed at the base and the lateral loads taken there?
 
Just another thought.
Paul.
Phoenix, AZ

 
On 7/17/07, Mauricio Castro <rico355(--nospam--at)hotmail.com> wrote:

Thanks Wesley and Josh for your promt responses. I should have shared a bit more information. This reactor is supported by four channel beams which are then supported by the 12 B 16.5 beams, which is where im having problems with. Example: A 12 B 16.5 beam has three piont loads acting on it and a dead load which yields reactions of 4.832 and 4.269 kips at the ends and a maximum moment of 7.947 kip-ft (the calculations are correct). It is only braced at the ends and the beam is 5' 6" long.


From: "Josh Comfort" <jcomfort(--nospam--at)ggbse.com>
Reply-To: < seaint(--nospam--at)seaint.org>
To: <seaint(--nospam--at)seaint.org>
Subject: RE: Maximum Moments in Beams
Date: Tue, 17 Jul 2007 08:01:42 -0700


It appears to me that unless you have a very short span your maximum moment might be calculated wrong if the beam is carrying a 13k load.
 
Can you give us more information, i.e. beam span, tributary area, basic loading...?
 
Josh Comfort, P.E.
Golden, Graper & Burton, Inc.
1500 W. Fourth Ave., Suite 509
Spokane, WA 99204
(509)624-3224 (509)624-3225 Fax
-----Original Message-----
From: Mauricio Castro [mailto: rico355(--nospam--at)hotmail.com]
Sent: Tuesday, July 17, 2007 7:27 AM
To: seaint(--nospam--at)seaint.org
Subject: Maximum Moments in Beams

I am currently revising the structure of the floor of a building to make sure that the old beams will manage to carry an increase in dead load of about 7/5 of the current load. I calculated the new maximum moments and compared them to the maximum moments allowed by the beam (Using my 13th edition AISC steel construction manual).
I am getting maximum moments of about 8 kip-ft and according to the manual these beams (12 B 16.5 which are supposed to be W12x16) should resist moments up to 75.4 kip-ft. This is a noticeable difference which makes me thing that either the beam highly safe or the calculations wrong. I haven't considered safety factors yet, but even then, the safety factor would be too high. The floor is the top floor and practically only carries the weight of a reactor (around 13kips) and unfortunately the only plans are the layouts of the beams.
 
Does this difference in maximum moments sound right?
 
Mauricio Castro
Civil Engineering Student
LSU


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