concrete column fixity

[calculor1]

In conventional two way slab construction the columns are poured first with the reinforcement extending above the slab. When the slab is poured do you consider the coonection as fixed or pinned? I have always designed the column for the unbalanced moment and axial load. A recent discussion with a more senior engineer, he treats the column as pinned. Do most engineers consider the connection pinned or fixed (or somewhere between)?

 

[JAE]

It should be considered fixed because that is what actually happens in the structure. Considering it pinned is OK for the slab, but the columns would be under-designed if you don't consider the moment induced into the columns.

....but now that I've said that, there may be implications with the column to slab connection - specifically the shear calculations over the column (slab to column punching shear) that takes moment into account in determining the shear stress in the slab directly surrounding the column.

 

[haynewp]

Yes, punching shear is related to the moment at the slab to column connection so it may not always be good to consider the slab as pinned at the column. Column to column is normally considered fixed.