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"Grade Beam" indoors

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ToadJones

ToadJones

Structural
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I have situation where I may need to design a somethign similar to a grade beam that would be indoors to support heavy traveling equipment.
In a case like this is there any need to go below the frost line or is down to suitable soils ok?
Would it be advisable to use small piers, say at 10' centers to support the grade beam rather than support the beam directly on the subgrade or prepared subgrade.

This is conceptual at this stage.
Any advice or input would be great.
 
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Interior footings and grade beams can be shallower - just need to get to good material. We use 12" deep interior footings all the time.

 
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JAE-
what if your foundation is near an exterior wall?
 
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Insulate between them? Or you make the interior footing deeper for a short distance and then transition up shallower.
 
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yes, the building will have heat; presumably always.

I just have intuitive concerns with only going down 12" or so in an older existing building. I have yet to look at the site, but I'm uncertain as to what kind of fill is going to be present under the existing slab. I'm not sure I'll be able to look at he fill and say "that looks okay".
 
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Normally for this situation we have a footing thickness of 12" or what ever is required and the top of footing is 8" below finished floor if they want to hide the anchor bolts/base plate (if there are any)and the slab is poured over the top. We also assume a reasonable value for Net Bearing Capacity say 2-3,000psf (sandy/clayey/gravel) and clearly state that this shall be verified by owner/owner's representative.

EIT
 
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Any pointers for design of a BOEF with point loads?
I guess really waht we are talking about here is not really a grade beam if there are no supports other than the soil, correct?
 
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I assume by BOEF that you mean a Beam On an Elastic Foundation analysis here?

If so, it would be very appropriate unless you can span the grade beam to existing footings, which you seem to say that you can't.

Mike McCann
MMC Engineering

 
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If the grade beam is a BOEF situation, then I would separate the slab from the grade beam with two sawcuts (used to install the beam) to let the grade beam work separately here. Otherwise, the slab will see cracking due to the moving load.

If this is a metal building (PEMB) you may have cross-ties or hairpins at the mainframe locations to consider in the design too.

Just a thought.

Mike McCann
MMC Engineering

 
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thanks Mike-
sorry to blur the lines.
I was thinking originally that maybe I would install piers and span the grade beam between. I think this is not practical.
I think it will wind up as a BOEF....Beam On an Elastic Foundation
or a
GBOEF....Grade Beam....
 
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Job has risen from the dead....

Mike-
Should I encounter Hair pins in the excavation am I screwed or can I incorprate them into the new beam?

Also, I'd like to ask again if others think a BOEF is an approapriate approach?

The beam will essentially bear on soil and have a series of moving loads.
 
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If possible, I would try to locate the existing hairpins and mark their locations on the slab so their integrity can be saved and integrated into the addition. Otherwise, you will undermine the integrity of the structure.

Mike McCann
MMC Engineering
 
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I may need to take a strip out of the slab that would be parallel to the existing exterior columns roughly 8' in from the columns. If I were to find hair pins at this location, and they passed through the removed section of slab or happen to terminate in the area where the slab is removed, is it possible to reincorporate them into my new foundation ?
 
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sorry Mike...I misread your last post at 22:31.
I see what you were saying now.
Thanks
 
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