On Sun, 20 Mar 2005 13:22:34 GMT, Rob Munach
wrote:

Brian Whatcott wrote:

On 18 Mar 2005 08:36:10 -0800, wrote:


That's why I figured I might as well overdo it.

I've now decided to go with a Steel I-beam (looks like it will be the
same or cheaper than lumber - but will make a much smaller header.)
Question now is, should I go with a 4" 6" or 8" IBeam? What iBeam size
would be equivalent to Three 2X12 at 13 feet??

Keep in mind, the only thing holding up the wall I plan on removing is
Two 2X12's


A specimen load for a 6X12 in wood beam at 13 feet is 200lb per foot
uniform loading, for which the max deflection is 0.1 inch This has a
safety rating of X2 to failure for reasonable assumptions:
Youngs 1.5E6 psi limit stress 1.2 kips

A steel I beam: W8X15 deflects 0.09 inches for this load,
a W8X13 deflects 0.11 inches.
Youngs 29E6 yield stress 36 ksi

Respectfully

Brian Whatcott Altus, OK
Brian,
You may want to re-check your calcs.

6x12 (assuming 5 1/2 x 11 1/4 - which is larger than the (3)2x12
specified) S = 116

For 200 plf over 13', M = 4225 ft-lb

M/S = 437 psi which is a little under 1/2 of what is typically used for
the design stress (which already has a huge factor of safety).

Regards,


Rob, the calcs aren't mine, they are the result of Archon's Beams
program which also checks against code.

I made explicit my inputs, as to Youngs, limit stress and dimensions
for both the wood beam and the steel beam.
You note that you used commercial "finished" dimensions rather than
gross rough-sawn, and that's a not unreasonable basis for the
difference in your wood beam calcs, I certainly agree.

Respectfully

Brian Whatcott Altus, OK