Help with BAD Prefab Building Foundation Drawings 2

[dmitriy555]

I got a set of foundation drawings for a prefab building from a prospective client. They said these drawings are from very good but pricey engineer, they want me to design foundations for other similar buildings. I started to review these drawings and found lots of mistakes and other items I need another engineer's opinion. The three pages are attached.
1. Is that ok to use rectangular ties in a circular pier?
2. Do I need ties in the pad portion?
3. If the pad is circular 3', shouldn't i place my reinforcement in radial pattern?
4. Do I need a curtain wall around the perimeter of the building extending below frost line?
5. Shouldn't I have foundation grid going through the center-lines of the foundations, instead of measuring from an building line?
6. why for detail C, F, G there are (8) #6 bars in the piers that are smaller in diameter than other piers, and those only have (6) #6?
7. why some pads are rectangular and some are trapezoidal? Any sense in that?
8. Is there a reason to have a pad for a foundation under a door column? the foundation does not carry any uplift load?
9. Does the foundation on page 3 needs reinf. with hooks for a spill over?

I know some of the questions may sound dumb, but I certain things i never seen to be in this way.
I do not have the original building reactions but suspect they are not high. Also, what would be a good price to charge a client for a similar set of drawings considering that it may be on a regular bases. Please post your answers and comments and have fun.

 

[hokie66]

1. Yes, the pier is only circular because of the type form used.
2. No.
3. A circular pad is silly, I don't know why it is not square.
4. The footings all seem to be about 5' deep, and there does not appear to be any floor. What would a curtain wall accomplish?
5. Why? Personal preference.
6. I don't know. Perhaps knowing more about the structure above would give a clue.
7. Didn't see either the rectangular or trapezoidal pads. Where are they shown?
8. Again, without knowing more about the structure above, it is hard to say.
9. These footings are for a "sound wall". Without knowing more about it, I wouldn't comment.

 

[msquared48]

I am really concerned with the quality of the foundation here.

There is no concrete slab, and no hairpins to tale anyh lateral. OK, but the holes for the piers are not augered, but dug and backfilled with material after the pier is poured, negating using the allowable lateral design pressure of the IBC as the material at the sides of the pier must be undisturbed.

I would be curious to see the lateral calculations for the foundation...

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[dik]

Missed this one...

Hokie's pretty much on the mark and more info would be required. Regarding Item 3, if moment resistance is the same in both directions, then this is the moment capacity at any angle. The slab is considered as isotropically reinforced. Reinforcing does not have to be radial. If different moment capacity, I don't know why for a circular pad. Don't know why a circular pad unless the footing has been drilled... most cases, a square pad as Hokie noted is OK.

Mike, the building footprint is pretty small and unless it is not very tall, the horizontal thrusts are likely minimal.

Dik

 

[msquared48]

True, but you can still get lateral kicks of 2 to 3 kips.

I always use hairpins to the slab in these buildings where there is a slab, and buried cross ties where there is no slab to control the lateral spreading. Just makes for a better structure.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[dik]

I like to use hairpins, too... they're most positive, but, sometimes the horizontal thrust must be resisted by the foundation... done that too...

Dik