Grade Beam Use 1

[gt2303a]

I have a project that requires piles for the foundation system. Due to the soil present, a structural slab is also required. I originally thought of supporting the concrete columns with pile caps, and the structural slab with grade beams that spanned into the caps. This design scheme worked well until I got to one side of the building. On this edge, I would need to design a zero-lot pile cap, with the column exterior face flushed with the edge of the pile cap. I'm concerned the cap won't work due to the column moments (the columns are all part of a concrete moment frame to resist lateral wind forces). Now I am thinking of supporting the columns on grade beams with piles under them. FYI, the structure is only a 2-story building. However, the lateral forces are significant (Florida).

Any thoughts? Should I stick with the caps and grade beams or only use grade beams?

Thanks for your help!

 

[Ron]

Yes! Stick with the pile caps and grade beams scheme. Grade beams are fairly rare in Florida...pile supported grade beams are certainly going to be an issue.

 

[msquared48]

As the ground settles, gators love to hide under the slabs.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[Ron]

Hey Mike...more accurate than you intended!!

 

[gt2303a]

Thanks for the quick replies! If I stick with the pile cap and grade beam scheme, how would you deal with the zero-lot pile cap? I'm a little concerned about the column base moment when is rotating away from the pile cap (towards the zero-lot line). To me, it is like a retaining wall without a toe!

Any ideas?

 

[Ron]

Not sure of your building configuration, but you could either move your column line in and let your grade beams cantilever to the zero lot line or you could get an easement to put the pile cap in over the line.

Keep in mind that eccentricity for a pile cap is not unusual.

 

[dik]

Can you use gradebeams with pilasters in lieu of pile caps on the property side?

Dik

 

[gt2303a]

Thanks Ron! The building is a straightforward rectangle. There is an existing building right on the property line, so I can't ask for an easement. The architect needs the open floor layout, so I can't push the columns into the space.

I'm currently needing a cap with (4) 14" dia piles. I can easily design the piles for the loads and moments, but I am worried about the column moment rotating away from the cap. I just do not see a way for the pile cap to deal with it without some "meat" on that side of the column.

 

[gt2303a]

Dik, that was the "solution" I thought about for my problem. However, it seems from previous responses that sticking with the pile cap scheme is a better solution for the GC. Apparently, grade beams are fairly rare in Florida. Any other thoughts?

Thanks for the help!

 

[msquared48]

Personally, I do not see a problem with insetting the pile and cantilevering the grade beam to the property line or setback line, providing the pile on the other end of the grade beams can take the uplift, if any. Sounds like the cantilever can't be more than three or four feet.

Oh, and Ron... I have been in Florida, but never lived there. I just know from experience up here that all sorts of varmits like crawlspaces - cats, rats, possums, raccoons, snakes... Just figured gators are no different as they are looking for food and shelter too - mainly food, like cats, rats, possums, raccoons, snakes...

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[Ron]

...and people!

 

[msquared48]

You said it. I didn't!

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[dirtsqueezer]

Are pile caps connecting grade beams more for the pile, or more for the grade beam? Just from one that doesn't know.

 

[dik]

I'd likely dispense with the pile cap if possible and extend the pile reinforcing into the pilaster of the grade beam; it's easy construction and common in these environs... might be strange in Florida... BTW, we don't have a problem with gators nesting in dark corners... our winters put them to sleep... and they doze right through the summer...

Dik

 

[msquared48]

Now, if we could get all those gators to doze during football season...

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[TXStructural]

Have you considered extending a beam under the slab to an adjacent pile cap and column, to take the moment for the zero-lot columns? Or, make your pile cap extend further under the building to put tension into the most interior piles (which may require one or more additional piles.)

 

[Ron]

Bite your tongue, McCann! Go Gators!!