[jackbequick]

I'm trying to figure out how what size beams I would need to hold a distributed load. The structure is 40 feet by 10 feet.

Length of beam is 16 feet. 3 feet of that beam on each end is supported by an earthen structure underground. So the actual load is only on 10 feet. The load is 35,000 pounds per beam and I will be using 20 beams.

I will have the 20 beams separated every 24 inches to hold the overall load. The overall load above the structure is 660,000 pounds. For saftey I will make it an even 700,000 pounds.

What size beams would I need to have a center deflection of only .5"?

[packrat]

Try this site for engineering calculations - Structural Beam Deflection and Stress Formula and Calculation - Engineers Edge I'm very math challenged, and even I can work out the loads and stresses.

[jackbequick]

Thanks.

I've been to this site before, but I wasn't sure if that is what I needed.

[RICHARD ZASTROW]

I hope your "earthen structure" can support the load without compressing.LOL

Dick Z

[jrm850]

I hope your "earthen structure" can support the load without compressing.LOL

Dick Z

This is my initial thought as well. If it were me I would emperically measure the density of the supporting earth and displace enough of it with the supporting pads to float the required load X safety factor. I would also think very hard about the 1.06 safety factor of 700klbs.

If you are 24" on center with a 3' long base your pad loading will be 40.5 psi using a safety factor of 2 and assuming unachievable perfect variables. (35klbs per pad/864^2") An anology would be like trying to jack a Cadillac Escalade completely off the soft ground using a bottle jack with a 1 sq ft base.

[keebler303]

I would guess that the .5" deflection requirement would require a beam that would give you a significant safety factor regarding yield strength. Buckling may also come into play depending on the beam you use. If the beam is placed on a less than solid support, the beam could roll, which will make it weaker and more prone to buckling. If this is a buried structure, you have to worry about corrosion, etc.

I would strongly suggest soliciting some help from a qualified Professional Engineer (PE) to reduce the likelihood that you or others will prematurely end up "6 feet deep"

Matt

[rowbare]

The overall load above the structure is 660,000 pounds. For saftey I will make it an even 700,000 pounds.

That is too much weight to dick around with. Hire a structural engineer who knows what he is doing.

bob

[Falcon69]

I did a projct awhile back. Built a roof over a deck.

When I took the drawings i had drawn up down to the permit office to get the building permit, The engineer there revised my drawing and took out extra support I had drawn up, out of the plans.

Try your local permit office. They may just have an engineer there that will revise your drawing for you when you apply for your permits.

[kiwibrick]

I'm a structural engineer, and I agree with a few people above, take your plans to a structural engineer in your area and let them do their thing.

8.3kPa floor loading is pretty significant, I'm guessing this will be a storage room of some kind? If so the factors can be different depending upon whats stored.
I would normally use 1.2 for deadloads and 1.5 for liveloads (form our codes here).
Also if there is flooring of some kind on top of the beams that would most probably need to be designed as well.