Point loads on a plate placed on a floor.

[mula1]

Hello all,

I have a question which I need a bit of help envisioning.

I have a heavy machine with 4 legs that i need to place on the floor, but I don't believe the floor will be able to withstand the point loads generated by each leg - The floor is suspended.

To solve this I wish to place a steel plate under the machine to spread the point loads of the machine legs across the floor. The plate will be fully supported by the floor i.e. there are no gaps in the floor.

What I need help with is how the steel plate will distribute the point loads, I'm pretty sure I will have diminishing circular stress spread from each leg? There may be overlapping stresses generated by each leg.

If I have maximum load capability of the floor, how can I convert 4x point loads on the top of the steel plate to work out the force exerted by the base of the plate to the floor?

I believe these calculations will help me find a suitable thickness of SS plate?

I have also thought about using 2x SS planks instead of a plate but I wish to start with looking at a plate first.

Many thanks for any help.

 

[ldeem]

It is difficult to get a flat plate on a floor to spread loads out to from a point. The problem is the plates ability to spread out the load is a function of the plate stiffness and the floor stiffness. If you look at some slab on grade point load design references it will help explain the concept.

If you need to stay above the floor it may be necessary to use beams to carry the load out to the main floor support beams. In this case I usually set steel blocks above the support to elevate the beam above the floor. If the machine vibrates you will need to check the natural frequency of the beam - you don't want the equipment sitting on a trampoline.

If your load isn't too high and you are on a steel composite deck the SDI "Composite Deck Design Handbook" has a concentered load between support joists example.

 

[WARose]

What is the floor made of? Reinforced concrete slab? Is one-way/two-way shear the problem?

Even with a very large plate underneath the columns....I wouldn't spread it out too far. It's one thing with a column base plate-where the dimensions are not that much bigger than the column-but a whole other ball game if you are intending to spread it out very far.

You may have to add some steel beams to the floor to directly pick up the column bases.