Thank you for a very illuminating explanation!
I was thinking only in terms of rigidity of the one dimension, which I know
varies as the square. ie, a 2x8 is 4 times as stiff as a 2x4, etc.
Thus, I thought the H position of a beam would be "additively" stiffer than
the I position, in the case where the flanges were the same dimension as the
web.
But the compression/stretching aspect of the flanges is an eye-opener, and
makes a lot of sense!
Bless you!
I mighta gotten myself into a fair amount of trouble down the road, as in:
Damn, what are all those cracks doing in my new concrete floor--and why are
the beams sagging????
--
Mr. P.V.'d
formerly Droll Troll
"Jerry Foster" wrote in message
...
"Proctologically Violated©®" wrote in message
...
Awl--
Been fooling around w/ this program/utility. Pretty neat.
Quick Qs:
For a W beam, you can orient it so that it looks like an "I" or like an
"H".
Which orientation does the X-X value for the moment correspond to? I
believe X-X corresponds to the "I" orientation, judging from comparisons
w/
channels, whose relative deflections is intuitively clear.
For a "4x13" W beam, whose flange width (4.060) is about equal to the
main
web depth (4.160), and considerably thicker (flange thickness .345 vs web
thickness of .280), the program indicates deflection in the H position to
be
*3 times* the deflection in the "I" position--about .311" vs. .106", for
a
10 foot beam supported at the ends, w/ a 1000 lb point load at the
center.
Does this make sense? I would have expected the deflection in the H
position to be only 1/2 the deflection in the I position.
Whazzup?
--
Mr. P.V.'d
formerly Droll Troll
Without getting into a lot of "stuff" one would expect less deflection in
the "I" position. For the beam to deflect, the upper plate has to stretch
and the lower plate has to compress. This is the primary contributor to
the
rigidity of the beam. The secondary contributor is the distributed
stretching and compression of the center web. In the "H" position, you
only
have the distributed stretching and compression of the sides and the
center
web contributes very little.
Jerry