Base plate thickness

Input

Bearing stress

w

Allowable bending stress

f_b

Projection length

l_{x1}

Fixed edge length of the projection

l_{y1}

Corner short side

l_{x2}

Corner long side

l_{y2}

Result

Side ratio of the projection

\lambda_1

Moment coefficient of the projection

\alpha_1

Bending moment of the projection

M_1

Required thickness of the projection

t_1

Side ratio of the corner

\lambda_2

Moment coefficient of the corner

\alpha_2

Bending moment of the corner

M_2

Required thickness of the corner

t_2

Required plate thickness

t

Notes

Based on the base plate check in 7.2(1)6), exposed column base, of the AIJ Recommendation for Design of Connections in Steel Structures. As in its Design Example 2, out-of-plane bending is checked by treating the part projecting beyond the column flange as a plate fixed on three edges and free on one and the corner as a plate fixed on two adjacent edges and free on the other two.
The moment coefficients were read off the stress charts in Appendix 10 (Figs. A10.3 and A10.5) of the AIJ Standard for Structural Calculation of Reinforced Concrete Structures. That book gives them as curves rather than a table, so They are not values transcribed straight from the source. Reading them off is good to about ±0.01 on the coefficient, which works through to roughly 2 % on the thickness because t ∝ √M.
The stress charts are titled ν = 0. That is the assumption used for reinforced concrete slabs and differs from ν = 0.3 for steel, but Design Example 2 of the Recommendation itself applies these charts to a steel base plate.
The side ratio can only be read between 1.0 and 4.0. The charts in the source cover no more than that, so outside the range the end value is used and the page says so.
The bending moment and section modulus are per 1 mm width of plate (Z = t²/6). This follows Design Example 2 of the Recommendation.
Work out the bearing stress separately and enter it here. the exposed column base page will give you the bearing stress on the concrete under the compression side of an exposed column base.
Work out the allowable bending stress separately as well. For short-term loading, take 50 % more than the long-term value (AIJ Standard for Allowable Stress Design of Steel Structures, 5.6).
To check one side only, leave the other dimension empty. The required thickness is the larger of whichever values are obtained.
Where the Standard writes "stress intensity", this page writes simply "stress".