Column Base Plate under Axial Load (AISC Design Guide 1)
The plan size and thickness of a concentrically-loaded column base plate: the required concrete bearing area A1_req = Pu / (0.65 x 0.85 x f'c), the cantilever dimensions m, n, and n', and the thickness tp = l x sqrt(2 Pu / (0.90 Fy B N)). A W10x49 at 400 kips on a 14 in square A36 plate over 4 ksi concrete needs a 1-1/8 in plate; raise the load to 700 kips and the tile flags the plate as too small in bearing. Concentric axial only; anchor rods and shear transfer are separate. A design aid, not a substitute for the engineer of record.
Formula and source
A1_req = Pu / (0.65 x 0.85 f'c); m = (N - 0.95 d)/2; n = (B - 0.80 bf)/2; n' = sqrt(d bf)/4; l = max(m, n, n'); tp = l sqrt(2 Pu / (0.90 Fy B N)).
AISC Design Guide 1 §3.1 and AISC 360-22 §J8, by name; the concrete bearing uses phi_c = 0.65 with the confinement factor taken as 1.0.
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