For greatest resistance to bending, as much of a plate girder cross section as practicable should be concentrated in the flanges, at the greatest distance from the neutral axis. This might require, however, a web so thin that the girder would fail by web buckling before it reached its bending capacity.
To preclude this, the AISC specification limits h/t.
For an unstiffened web, this ratio should not exceed.
where Fy = yield strength of compression flange,ksi (MPa).
Larger values of h/t may be used, however, if the web is stiffened at appropriate intervals.