Originally Posted by DennisCNC ^^ I measured the shop and it is 45' not 50' so thats a plus. I will use it move granite slabs around, from the cart to the saw and so on. Maybe my 3K lbs estimate is a little high. The slabs weight is 1,200lbs. max plus the winch, trolly, vacuum lifter, I think that will be another ~700lbs. So I think a better estimate would be 2,200 lbs. max load. This load will mostly be in the middle.
I can make the trolly support wheels farther apart to spread the load. If I happen to need to move something heavier i'll just use the forklift. With the over head crain one person can move the material around. |
Dear Dennis,
unterhaus is right on the button with with comments on buckling.
If the top flange of the I beam is not restrained (ie prevented from moving sideways), and you have a clear span of 45 foot, the permissible bending stress for the beam will be far less that the nominal value for the steel. In order to get round this problem, you have to go for a larger section.
I have not done steel calculations for a while, but I thought I'd have a go.
My conclusion is that if the ends of the beam are not built in to something substantial, and if the top flange is not restrained, the major factor is keeping the bending stress to acceptable limits. If you have a beam of steel which has a basic permissible bending stress of about 23000 lbs per square inch, by the time you make allowances for the span and the lack of restraint, the actual bending stress that the beam can handle is down to about 6100 lbs per square inch under these conditions.
If my calculations are right (and it is possible they are not) you might consider this beam....
24" deep
9" wide
top and bottom flange thickness 11/16"
web thickness 7/16"
beam self weight 225 lbs per yard
The steel should have a basic permissible bending stress of at least 23000 lbs per square inch.
The total deflection at mid span (including that due to the self-weight of the beam) will only be a little over 1/4". The bending and shear stress are within limits but I have not checked for
web crushing and buckling.
Finally, please don't go ahead and use this beam without getting a structural engineer to OK it. I can't afford the lawyers fees!
Best wishes
Martin