The ANSI/AISC 360-16 Specification for Structural Steel Buildings does not provide any specific procedure to design column base plate. However, the design process of steel column base plate is discussed here based on the design examples given in the AISC Steel steel construction manual.
Learn more: Steel column base plate [EXPLAINED!!]
Design of a steel column base plate
Design area of the column base plate

The design strength of the concrete in bearing beneath the base plate must be at least equal to the load to be carried. Let A1 be the area of base plate and assuming that entire area of concrete footing is covered with base plate. In that case, the nominal bearing strength of concrete (Pp) is
Pp = 0.85 fc’ A1
fc’ is the 28 days compression strength of concrete.
In case when the area of concrete footing is greater that the area of bearing plate, the concrete underneath the plate would be somewhat stronger due to the surrounding concrete. In that case, Pp can be increased by the factor, where A2 is the the area of concrete footing. The maximum value of √A2/A1 is limited to 2.
Pp = 0.85 fc’ A1√A2/A1 <= 1.7 fc’ A1
The minimum value of A1 is width of column flange bf times its depth d.
The aforementioned two equations are given section J8 of the specification
Design thickness of the column base plate

To calculate the design thickness t, moments (shown in the equation below) are taken in the two directions as though the plate were cantilevered out by the dimensions m and n shown in the figure A.

These moments are then compared with the flexure capacity of the steel base plates to compute the thickness.
By this method we get very small thicknesses (unrealistic) for lightly loaded columns
In such cases, more practical approach is the Thornton method, which uses following equation to compute bending moments


Read more: How to calculate the design capacity of a steel column? [Step by Step guide]