How to find thickness of steel plate

[Ron1808]

I have a 300 mm diameter hole in the ground surrounded by concrete. This hole will be covered by a steel plate. I need to get a machine of weight 2.5 tonnes across this hole safely without any bending of the steel plate.
How would i calculate the required thickness of the plate?
Thank you
Ron.

 

[Bystander]

The machine is on a skid? Rollers? Wheels? Casters? How is the load distributed?

 

[Ron1808]

It is a brokk, so it will be tracks. As the brokk may carry stones etc, I am assuming a point load distribution for worst case scenairo.
Thank you

 

[Bystander]

A Brokk. Down a one foot hole? You've got a copy of Machinery's Handbook handy? Look at diaphragm deflections in the strength of materials section. Pick what deflection you can live with and back out the plate thickness.

 

[Ron1808]

I don't have the handbook with me but i will have a look at it later when i go home. But thank you for your help and advice. :)