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Floor Loading

Floor Loading

Floor Loading

I am trying to determine if there is a standard methodology for calculating floor loading for heavy machinery? I have a 3832 lb gantry to be supported on a concrete floor in a hospital. The gantry is mounted on 4 vibration isolation pads. The two front pads have a 4.5" diameter surface contact (15.9 in^2), and the two rear pads have a 3.5" diameter surface contact (9.6 in^2). The front two pads take 1556 lbs each, and the rear pads take 360 lbs each. The total area under the outer edges of the foot pads is 30" x 56" = 1680 in^2 = 11.67 ft^2.

How do I calculate the floor load spec for the gantry?

Is it the total weight divided by the area under the outside edges of the foot pads? 3832 lbs / 11.67 ft^2 = 328.6 lbs/ft^2?

Is it the max point load from each foot pad? 1556 lbs/15.9 in^2 = 97.86 lbs/in^2 = 14092 lbs/ft^2? (this seems insanely high).

The only floor load specification calculation example that I have is from an IBM site preparation manual that uses service load and static load areas, as well as live load and static load constants.

Any suggestions would be appreciated.


RE: Floor Loading

In my view, you design the general floor for the loads that to its use correspond + the loads coming from the gantry. If the gantry loads include the effects of imapc etc, the gantry is portraited as 4 point loads for the gneral structural model. This done, it is always sound practice to put something of substance under point loads. A full section of slab can be right, and also beams of proper strength. This is far better than letting fall the load anywhere in a floor built who knows in what way.

By using the general load for the use the room will be reutilizable when the gantry is someday in the future dismantled.

Respect the supports of the gantry themselves one needs to care the slab has enough shear punch capacity, what you may do as per the applicable code. To all other effects representing the loads as point loads will be enough.

RE: Floor Loading

I believe the equation you are looking for and one that can be used to determine loading (in this case compressive loads) is:

P = Af


P = load, (lb)

A = cross-sectional area (normal to load) for tensile or compressive forces, or contact area for bearing loads (in^2)

f = tensile, compressive, shearing or bearing unit stress (psi)

A bearing point of 15.9 in^2 on a concrete slab 3,000 psi = 47,700 lbs. 14,092 lbs does not seem much.

RE: Floor Loading

Use the concentrated load from each pad to determined size of beams.  The concentrated loads must include the effect of the maximum overturning moment which in all likely hood will result in an uplift effect on the rear pads unless measures are taken to counterbalance or resist the overturning moment.

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