turndown slab foundation
turndown slab foundation
(OP)
Does anyone know what is meant by "a shallow monolithically-placed turndown slab foundation". This phrase has turned up in a geotechnical report that I am currently reviewing. The report was written to provide geotechnical recommendations for design and construction of a natural gas station, which will include the use of precast concrete buildings (similar in size to a mobile home and/or construction trailer). The turndown slab foundation was recommeded for use with these buildings.





RE: turndown slab foundation
RE: turndown slab foundation
RE: turndown slab foundation
1. If there are heavy wall loads on the turned downed section of slab, the deflections of this part will likely be greater than that of the rest of the slab and significant cracking and differential settlement can occur.
2. The downturned section will act to restrain slab shrinkage and unacceptable cracking can occur unless proper control joints are detailed.
RE: turndown slab foundation
RE: turndown slab foundation
RE: turndown slab foundation
********************************
*
* *****************
* /
* /
* /
************
Something like this!
Be aware that scouring can be a problem with this type of slab system.
RE: turndown slab foundation
RE: turndown slab foundation
RE: turndown slab foundation
Thanks,
---
Andrew
RE: turndown slab foundation
Regarding scour....this is when runoff from the roof or surface cross-flow removes the soil adjacent to and under the bearing edge of the thickened edge, causing a loss of bearing (cantilevered edge).
RE: turndown slab foundation
RE: turndown slab foundation
Usually, the perimeter beams are supplemented with an interior grid of beams to form what is called a "stiffened slab-on-grade". The beams are spaced between 12 ft. and 16 ft. on center and are usually 12 to 18 inches wide and can get as deep as 36 inches (even in non-frost areas). The concept is to create a rigid mat on which the building rests.
A design methodology has been developed by the Concrete Reinforcing Institute in conjunction with The Wire Reinforcing Institute. It was prepared by Walter L. Snowden, P.E. in Austin, Texas back in the 70's (I think).
I have the document which is titled "Design of Slab-on-Ground Foundations, A Design, Construction, and Inspection Aid for Consulting Engineers", dated August, 1981. I would hope that there are copies available through a search on the internet.