Is this a beam , a slab, or something else?

[bridgebuster]

I have to design a 12'x 12' concrete cap for an 8-foot diameter HDPE manhole - sketch attach. The cap will support HS-20 loading; and it has to be supported on fill per the manufacturer.

I'm thinking of designing it as a simply supported beam 10'long in both directions. I would do it this way if it were a concrete vault supporting the cap. Or should I consider this a beam on elastic supports? I looking for a simple approach - no FEA - the contractor want to build this thing on Monday.

Thanks for your assistance.

 

[dik]

That's a pretty healthy load for something reduced the way it is. I'd treat it as a beam two... and put 45 deg bars to finish trimming off the circular opening to match. I'd also thicken the edges to increase the depth and to help contain the soil.

Dik

 

[ishvaaag]

Do you remember the rule of at least 2.5 times the weight for dynamical loads? ... yes, this is not a machine, but insets on the roadway sink and move, some kind of failure, no doubt. Your contractor and property quite likely don't worry about this, they will be already fed of seeing the problem anywhere.

It is relatively easy to make the drawing with 3D Faces in autocad and pass the dxf to RISA 3D or SAP2000 ... make the elements modular so that you can easily place the wheel loads at your convenience, on elastic supports, then assign reinforcement.

 

[bridgebuster]

Thanks for the replies. I decided to go the conservative route and treat it as a beam.

 

[dicksewerrat]

Is your hatch HS-20 rated? What about your connections from the hatch to the slab? What is this for? Pump station?

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[bridgebuster]

Yes this is a pump station; and yes the hatch (which is 76" x 42") has to be HS rated. Although the choice of the hatch is up to the contractor.