FYI - Slabs on grade like patios are not considered structural unless it carries a load like a deck support column. In that case the slab becomes structural and requires an engineering design. If the deck column is supported by a concrete pier that penetrated the patio slab with an isolation joint then the patio slab is considered non-structural. If a patio slab was poured on top of a concrete pier and the deck support column sits on top of the concrete patio slab, then the patio slab becomes part of the concrete pier/deck column system, which is structural.
There are three different structural equations involved: (1) if the column is on the corner of the slab. (2) if the column is on the edge of the slab a minimum distance from the corner. (3) when the column is on the interior of the slab.
