Look at the standard specification, check the application first, chemistry and mechanical properties to verify if fit your aplication
The design is based on yield strenght, in this cases is the same strength, I suggest check the elogation and weldeability based on chemistry
A 572/A 572M Standard Specification for High-Strength Low-Alloy Columbium-Vanadium Structural Steel
Structural steel shapes, plates, sheet piling and bars..... intended for riveted or bolted construction bridges or for riveted, bolted or welded construction in other applications
plates and bars maximum thickness depends of the grade i.e. Grade 60 Plates and Bars 1.25 in
C 0.21-0.26
Mn 1.35
P 0.04
S 0.04
Si 0.15-0.4
Yield w/r grade i.e Grade 50 Yield 50 ksi
Tensile
Grade Yield Tensile Elongation
50 50 60 18%
60 60 75 16%
A 656/A 656M Standard Specification for Hot-Rolled Structural Steel, High Strength Low-Alloy Plate with improved formability
for use in truck frames, brackets, crane booms, rail cars and similar applications; killed steel fine grain pracice, Grade 50 plate thickness max. 2 in
C 0.18
Mn 1.65
P 0.025
S 0.035
Si 0.6
Va 0.08
N2 0.02
Cu 0.008-015
Grade 50
Yield 50 ksi
Tensile 60 ksi
Elong 20-23 %