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Need information on odd size I beams (S beam) I just acquired-

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lvbutcher

Structural
Feb 9, 2020
7
I just bought a pair of used I beams (S type, not H/WF)that I can't seem to find in any structural steel lists. I bought them from a scrap yard to build a small bridge over a creek on our property.

They are 20"h x 6.25"w (flange)x .50 web thickness. I was told they came from an old building in St. Louis and served as one of a set of double-beams that supported a water tank at the top of the building, as was done in the old days. I haven't run them over a scale yet, but the man I got them from told me they have a combined weight of around 3,500#. The only thing close I've found at 20" even is a 20" x 6.25 x .795". Also found 18" x 6.25" x 1/2" web. These beams are still bolted together with stiffener/spacer plates which are sandwiched between the beams, so I can't say yet exactly what they're made up of. As I said, they're old, but not old enough to still have used rivets, although the bolts are square head as opposed to hex head bolts. The beams are 28' 3.25" and 26' 9.25". Can anyone refer me to a reference sheet that may let me know exactly what size and weight (per foot) these are? I was assuming they were 65# per foot, which would have matched with the 18x65# per the 3500# estimate I was given. Now I don't know, and I can't find a true comparison list. BTW, I'm a retired structural Ironworker (retired, local 396) and a former welding instructor for the locals apprentices. It drives me crazy when I find a piece of steel I can't identify (this is the first), so I'm coming to the one's who know more than me. Not my wife. Engineers. Thanks, Lee Butcher

FWIW- In the pics, the two 50 gallon barrels in front are filled with water as counter weights for the 8' of steel that was hanging over the rear of my 20' trailer. I thought there would be 6'(x2), since the short beam was on top when I first saw them, and the 830 pounds of water weight would counter the calculated 780# overhang if they are, indeed, 65#/ft. I underestimated by about 80#. Luckily, the axles are to the rear of COG, so the 64 mile ride home on hilly, curvy Missouri back roads wasn't too bad. Thanks again for any clues on this steel.

"Knowing is not enough, we must apply.
Willing is not enough, we must do."
Goethe
 
 https://files.engineering.com/getfile.aspx?folder=74ee1352-1c0a-4bc2-8b7b-af2e912291da&file=Photo566.jpg
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That's it. The chart that I found that on listed the .795 dimension as web thickness, not the flange, and showed no .50 dimension at all. When I searched your entry, it brought up the info on the Engineers Edge site. Thanks very much, azcats. I felt ignorant before. Now I just feel silly. Much obliged. (I actually checked about 4 different charts, but they didn't show anything but WF, smaller beams or just had .795 as the web thickness. Thanks again! Lee

"Knowing is not enough, we must apply.
Willing is not enough, we must do."
Goethe
 
This still seems a bit odd to me, since the charts I've looked at show the tf, or flange thickness, measured at the outer edge of the flange, which on an I beam would be the least thick section. That would mean, at .795, that the outer edge of the flange would be over 3/4" thick. That can't be right. So, does this mean that an I beam's flange thickness measurement is taken from the center of the flange depth, not the outer edge?

"Knowing is not enough, we must apply.
Willing is not enough, we must do."
Goethe
 
lvbutcher said:
So, does this mean that an I beam's flange thickness measurement is taken from the center of the flange depth, not the outer edge?
Yes.
 
Ok. Thanks Jed! Seems the folks who draw up those dimension reference lines would know better than to place the lines at the thin edge of the part, not at the thinnest section of it. I'm learning quite a bit from this question.

"Knowing is not enough, we must apply.
Willing is not enough, we must do."
Goethe
 
Looks like a S20x65.4
Found in the 1970 CISC handbook, but not available from Canadian mills.

d = 20.0
Flange 6.25" x 0.789"
Web 0.5"
Total Area = 19.2 in^2
Area dw = 10 in^2
Ix = 1180 in^4
Sx = 118 in^3


BA
 
Ivbutcher said:
The chart that I found that on listed the .795 dimension as web thickness, not the flange, and showed no .50 dimension at all.

The flange thickness is listed as the mean thickness. Funny thing is, in my book it is listed as both as a decimal and a fraction, 0.789" or 13/16". But 13/16" is 0.8125" which is a bit more than the decimal value listed.

The web thickness is definitely listed as 0.5" and that is confirmed by the dw dimension (web area) of 10.0 in^2 (20*1/2 = 10).

BA
 
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