They used to service the cranes from British Steel regularly. One I remember was a ten ton static hoist that only performed one lift every year. It lifted the lid off something and put it back again.I beams have essentially a larger section modulus than a tube,
I have tinkered with a matterson gantry crane, it was the teeny tiny 500 ton version, I remember load testing with steel slabs, 1200 tons worth, the surveyor was on the top beam to check the deflection, it went from a positive camber to flat ( apparently going negative would be very bad) it’s still in service though the switchgear and motors have been changed, rope changed every 12 months, quite a job with 54 falls on each end of the lifting beam, quite a big spool of 2” cable.
Mark
The I beam was revolutionary in development of high rise architecture. Pipe hardly goes beyond getting fluids where they belong.It’s quite simple. Most of the metal in the tube is not where you need it. Most of the metal in a I beam is exactly where you need it.
A rectangular tube would be more expensive to makeA rectangular tube would have the same advantage, wouldn't it?
That makes sense but the tube rollers must be making bank, selling material for four times the cost of buying it for just rolling and welding it. This wasn't even pressure rated or certified material, and could likely be rolled cold.In order of cost increasing:
Flat Strip
Angle Iron
Channel
I-Beam
H Beam
Pipe (mostly made from flat strip)
Rectangular/Square tube (rolled from round tube/pipe)
Same for torsion strength in increasing order except Rectangular/Square is less not more.
If most square tube is made from steel pipe then I agree, it's going to cost more than steel pipe to get the same torsion stiffness. You get a small benefit in stiffness by weight from squishing a circle into a square but you loose some strength due to force concentration in the middle of the flats.In order of cost increasing:
Flat Strip
Angle Iron
Channel
I-Beam
H Beam
Pipe (mostly made from flat strip)
Rectangular/Square tube (rolled from round tube/pipe)
Same for torsion strength in increasing order except Rectangular/Square is less not more.
I found in simulations that straight square tube is very good at resisting deflection, but but a bent square tube (mandrel bent or rolled, not kinked) is very bad at it because the large flat areas are unsupported and tend to cut the corner, and deflect to a broader radius at very little load that puts all of the stress on the side walls and corners.If most square tube is made from steel pipe then I agree, it's going to cost more than steel pipe to get the same torsion stiffness. You get a small benefit in stiffness by weight from squishing a circle into a square but you loose some strength due to force concentration in the middle of the flats.
The difference between a square tube and a pipe of equal weight isn't particularly large, but a square tube of equal wall thickness compared to a pipe is significant difference because the square tube weighs 4/pi more and has more outer edges located 41% further away from the centroid, where their contribution matters (1.41^4) more.
There can be great differences between torsion stiffness vs strength, squishing a pipe into a rectangle of 2:1 length to width ratio would reduce it's torsional strength significantly but it's stiffness might be similar.
I believe the cheapest method to get sufficient torsion stiffness for an I beam gantry is to simply weld two I beams together to make a closed box section, let the gantry roll on the exposed flange. Or my other suggestion of make your own box beam with 4 flat bars welded into a sort of double web H beam
Why not post up some screen shots ?I found in simulations that straight square tube is very good at resisting deflection, but but a bent square tube (mandrel bent or rolled, not kinked) is very bad at it because the large flat areas are unsupported and tend to cut the corner, and deflect to a broader radius at very little load that puts all of the stress on the side walls and corners.
I'll run some fresh simulations to better show the effect. It surprised me quite a bit the first time I was trying to figure out why my stress concentration was so high.Why not post up some screen shots ?
I think you want strength in bending, not torsion, no?If most square tube is made from steel pipe then I agree, it's going to cost more than steel pipe to get the same torsion stiffness. You get a small benefit in stiffness by weight from squishing a circle into a square but you loose some strength due to force concentration in the middle of the flats.
I believe the cheapest method to get sufficient torsion stiffness for an I beam gantry is to simply weld two I beams together to make a closed box section, let the gantry roll on the exposed flange. Or my other suggestion of make your own box beam with 4 flat bars welded into a sort of double web H beam
depends... some flatbeds have I section frame rails, (BTW, top and bottom are called flanges, "diaphragm" is the web) but most new enclosed trailers use formed C section. they are formed from heat treated alloy for improved S/W ratio.Semi trailers have I beam chassis ,top and bottom plates are 3/4 or thicker ,the diaphragm is only 1/8"...........stiffeners are rarely used as they add to production cost........in any case the deck structure acts as. bracing.........if the frame does bend ,the trailer simply collapses..............back in the day ,trailers had a lower tension member ,similar to a railway wagon,except the railway wagon always had a turnbuckle that could be tightened to maintain the camber of the frame ........the trailer had a steel strap that could be tightened by cutting and rewelding.
For some things you want both torsion and bending, and the cheapest way to get it in my opinion is either weld a double web I beam from flat plates (spacing the two webs as far apart as you can, or weld two I beams side by side. On top of each other wastes the material in the flanges in the middle. You might as well have made a castle beam from a single I beam. (Cutting the web in a truncated triangle pattern and then welding back together shifted a bit with a deeper web)I think you want strength in bending, not torsion, no?
I would think the strongest beam would be stacked one on top of the other then welded rather than side by side. The load carrying of taller beams usually increase exponentially in height rather than width. IOW in wood a 4x16 carries more load than an 8x8
Not that welding beams together makes a lot of sense unless you already have a bunch of them
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