Concrete Column Unsupported Length
Concrete Column Unsupported Length
(OP)
I am double checking what the standard practice is for determining the unsupported length of a concrete column on the first storey of a building (without getting in to anything like horizontal soil springs, etc) .
I have a situation where my footing was lowered about 9' below the slab on grade to accommodate some piping. Is the unsupported length from:
A) the underside of the slab to the top of the footing
or
B) the underside of Level 2 slab to the slab-on-grade. The slab-on-grade is 5" thick with mesh and the soil is properly compacted.
I have a situation where my footing was lowered about 9' below the slab on grade to accommodate some piping. Is the unsupported length from:
A) the underside of the slab to the top of the footing
or
B) the underside of Level 2 slab to the slab-on-grade. The slab-on-grade is 5" thick with mesh and the soil is properly compacted.






RE: Concrete Column Unsupported Length
DaveAtkins
RE: Concrete Column Unsupported Length
If that is the case than both would be the unbraced length but worst case I think would be B. But you can only use the slab as lateral support if it is tied into the column with reinforcing.
RE: Concrete Column Unsupported Length
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.
RE: Concrete Column Unsupported Length
And I would use 3' because that seems to be a common assumption where fixity is assumed for the lateral restraint of piles.
RE: Concrete Column Unsupported Length
RE: Concrete Column Unsupported Length
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.
RE: Concrete Column Unsupported Length
I would rely on the soil to provide the lateral restraint required but wouldn't try to create a rotational fixity of the column.
RE: Concrete Column Unsupported Length