Tuesday, July 17, 2007

RE: Maximum Moments in Beams

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@hotmail.com]
Sent: Tuesday, July 17, 2007 7:27 AM
To: seaint@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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