Generator Slab

You need an experienced structural engineer.

Where are the bearing points on the deck?

Is the strength of the beams sufficient? If yes, how do you know that?

What are the starting and braking torques?

Will there be a sympathetic vibration problem?

I think 6" will be light for this unit. We installed a 750Kw, 10V @ 25,500Lbs this past fall. The manufacturer recommended a 10" steel reinforced pad. The clients project engineer demanded a 12" steel reinforced pad. The client's project engineer won,

Probably best to check the factory documents that were shipped with the unit. Most have a section outlining pad and installation requirements.

If you don't have factory docs call or e-mail tech support at Detroit. They will be more than happy to help you with this.

Good Luck

Hello Guest,

I just ran some quick calculations.

First, if you strictly used the GenSet dimensions, that equals 198.31 square feet. With a deal load of 33,000 pounds that equates into a 166.4 PSF bearing pressure from the generator alone. If you add the slab weight that brings the soil bearing pressure to at least 241.4 PSF.

For mechanical equipment with rotating or oscillating internal parts like motor, pumps etc I like to add a Impact Factor = 1.33 (conservative) to the equipment dead load. That now brings the total soil bearing pressure to:

qu = [(1.33 * 33,000#)/198.31] + 75 PSF Conc. Wgt. = 296.88 PSF

Since you haven't provided any description of the type of soil and it's condition to us I have no way to determine the Presumptive Soil Bearing Pressure to compare it to the total Soil Bearing Pressure. But I can say this, the SBP of nearly 300 PSF is fairly low compared to most allowable soil bearing pressures, unless of course you're building this slab on clay soil, slity soils, saturated soils, organic soils like Peat, Artic Tundra soils. You haven't told us where you are located either and if winter frost is prevalent in your area. Just make sure you construct the equipment slab on well graded and well drained compacted soils. I'd suggest no less than a 6 inch minimum thickness of clean organically free Run-Of-Bank (ROB) gravel subbase under the slab that is compacted to a minimum 95% Modified Proctor Density. Also, increase the slab planimetric dimensions at least 6-inches all around the equipment case.

As far as rebar goes using a minimum Shrinkage & Temperature steel requirement for the slab:

Min. Ast = 0.0018 * 6 * 12 = 0.1296 Sq. In./Ft. of slab width (say 0.13 Sq. In./Ft. width each way). Therefore, using #4's @ 12"o/c Each Way is more than adequate at 0.20 Sq. In./Ft Width. Of course you may use the #5's instead, which may aid in the concrete shrinkage problems.

You don't need the steel rebar for bearing conditions due to the load soil loading.

I hope this helps you. good luck with the project!