You would also have to add the weight of the beam which will deflect .09 inches by itself.
ksimolo, nice job, what size beam did you use on yours?
Gantry for Barn
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You would also have to add the weight of the beam which will deflect .09 inches by itself.
ksimolo, nice job, what size beam did you use on yours?
OP
SpringHollow
Elite Member
I thought those values took into account their own mass. Shows what i know. I used W10x15 So for the loads i quoted, one would have to subtract 300 lbs to get the live load for that deflection. I have not calculated a failure point for my setup.
Ken
Ken
OP
SpringHollow
Elite Member
Actually, if the weight of the beam is not in the values used, one would subtract less than the 300 lbs because the beam is not a point load.
Ken
Ken
To get the deflection of just the beam, I used the formula for Simple Supports for a Uniform Load, not a point load. So with the W14x22 and a 32 foot span, the beam just hanging there would have a maximum deflection of .09 inches at the center. Any additional load would cause it to deflect more.
For W10 x 15 and a 21 foot span, I get a maximum deflection of .033 for the weight of the beam itself using the uniform load calculation. It doesn't affect your situation much, but with a heavier beam and a larger span it starts to factor in.
chriswheeler
Platinum Member
Very nice work. For safety sake, when you are done, do a load test. Easy to do, center the whole thing with the trolly in the center of the beam. Rent a load cell if you don't have access. Load to 125% of what you are going to rate this thing to lift. Generaly chain falls will do this, 25% above their rateing. You'll thank yourself not having to ever wonder if something might ever come down at a bad time. Use a tractor or anything else that is properly rigged for a dead man between the load cell and the chain fall. Stay well clear during the test, leave the load suspended at 125% for at least 15 min. Your work looks good and more than stout enough, but I've had the misfortune to witness some bad accidents with this stuff, test is good insurance.
Chris
Chris
OP
SpringHollow
Elite Member
Hi Chris,
That is very good advice. The heaviest load i expect to have is a one time load of 2500 lbs. So i will stand far to the side when lifting that. If that holds, then i should be fine. So far, at 1100 pounds, it rolls extremely easy in all directions.
The other load test i had thought about was lifting my tractor at about 4000 lbs. That would have been neat just for the visual effect and a nice way to add air to the inner duals. But I am a wimp and believe in overbuilding and underusing.
Ken
That is very good advice. The heaviest load i expect to have is a one time load of 2500 lbs. So i will stand far to the side when lifting that. If that holds, then i should be fine. So far, at 1100 pounds, it rolls extremely easy in all directions.
The other load test i had thought about was lifting my tractor at about 4000 lbs. That would have been neat just for the visual effect and a nice way to add air to the inner duals. But I am a wimp and believe in overbuilding and underusing.
Ken
jimmer2880
Platinum Member
Thank you for all of those calculations as to what size beam I would need. I wasn't expecting those. Now, for the dumb question. How much would that beam weigh? Before deciding to go with such a beast of a beam, I would need to determine if I could get it up there once I bought it.
OP
SpringHollow
Elite Member
The first number is the depth of the beam, the second number is the weight per foot.
So W14 x22 is 14" deep and weighs 22 lbs per foot.
Ken
So W14 x22 is 14" deep and weighs 22 lbs per foot.
Ken
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The allowable stess falls rapidly depending on the unbraced length of the beam top flange. The beam will fail in lateral-buckling before it fails in bending, especially in a configuration like a bridge crane. It is dangerous to use elastic stress analysis without taking into account the allowable stress reductions for the un-braced length. For a W14x22, the allowabale stress needs to be reduced for unsupported lengths over 5.6'. In other words, the W14x22 used as a bridge crane beam for spans over 5.6' will fail due to lateral buckling, not bending.
The allowable stress for a W14x22 spanning 21' between lateral supports has an allowable stress of 5.7ksi, which is approximately 25% of the allowable stress for the same member laterally supported at 5.6' intervals, assuming A36steel.
Reference AISC (American Institute of Steel Construction), Allowable Stress Design, 9th edition.
Hope this helps
The allowable stress for a W14x22 spanning 21' between lateral supports has an allowable stress of 5.7ksi, which is approximately 25% of the allowable stress for the same member laterally supported at 5.6' intervals, assuming A36steel.
Reference AISC (American Institute of Steel Construction), Allowable Stress Design, 9th edition.
Hope this helps
