12x136

0 views

Skip to first unread message

Argelia Long

unread,

Aug 3, 2024, 4:51:31 PM8/3/24

to esevtihou

Kind of an informal "rule-of-thumb" about structural steel for a single span with end supports: Beam depth in inches should be half the span in feet. So for a 28' span, a beam depth of 14" is a minimum.

Just for the heck of it, I thought I'd run the thing. But the beam progrogram I have doesn't have a 12X136 in it's database. You never did answer my question as to whether this was clear span or not.
I don't remember being absent minded.

>> But the beam program I have doesn't have a 12X136 in it's database.Can you enter data manually? Machinery's Handbook gives the following data for a W12x136:X-X axis, parallel to the flanges
moment of intertia: 1240 in.^4
section modulus: 186 in.^3
radius of gyration: 5.58 in.Y-Y axis, parallel to the web
moment of intertia: 398 in.^4
section modulus: 64.2 in.^3
radius of gyration: 3.16 in.

The program I have doesn't allow for manual entry of design values. I have a book for hanf calcing steel beams, but I haven't seen it since we moved.
When I was little, my Mom used to make me stand in a closet for five minutes without moving. She said it was elevator practice.

The beams spanning my basement (32') are W10x22. If I had gone to a 16" deep by 50-something weight per foot, I could have clearspanned the entire basement. As it is, they deflect under their own weight and the weight of the floor deck by about 5/8" in the center, unsupported. As it is, there will be two posts at 12' from each end to support the timber frame, so the defelction will be minimal.

Gut feeling is, somebody really fouled that one up. Probably someone fresh out of college who ran the calcs without really thinking about the end result. If you plug in numbers without understanding the finished product - you can wind up with a very poorly designed end result, or a safety factor of about 10.

It is amusing to see fun poked at engineers and architects from the building trades.Do you ever wonder who they poke fun at?One answer (from my engineering student roommates in college):Just like we poke fun at them, they poke fun at the mathematicians and physcists. There are lots of good engineer and mathematician jokes where the engineer is the practical one and the mathematician the fool.Of course, now I wonder who the mathematicians make fun of?

MA in MAth. Interesting that it's an "arts" degree rather than a science (MS) degree. I use math all the time in my contracting work. I recently picked up "Workshop Math" by Robert Scharff. Good stuff.--B.C. (BS in Forest Ecology) now I'm finding out what happens with the trees after they cut them down.

I helped a guy build an addition on his house. He insisted on building forms for the footings instead of just digging trenches (his way was probably better), but he also insisted that where there would be "point loads" like on each side of where there would be a door or window, we had to widen the footings. I tried to explain that it would be easier if he had doubts about the footing width to support the load to just widen all of the footing because it would be acting as a beam anyway. Nope, we made jogs in the formwork. Right after that it rained hard and filled the forms with mud and clay that we had to dig out a second time. But on the roof sheathing, he left it on one side protruding about 2-3 inches past the ridge and got mad at me for wasting time when I cut it off.

I had house movers lift my house. They used a pair of W12x75 by 48 feet long, and cribbed near the ends of them, so the span was about 35 feet. There was almost no deflection in the beams, and the mover estimated the weight of the house at 30 tons, so that's 15 tons evenly distributed on each beam.