design code for structural steel

[Asya]

Bidders propeses ASTM A36 material istead of S275 J2 or S355ML/NL for structural steel (Piperack, Equipment Structure, etc.) on the basis of international standards for most optimal and economical design. Is it really optimal? pls explain why

 

[delagina]

We usually use A992 for W beams and A36 for channels and angles in the US for piperack, equipment structure, etc..
I don't really know which is optimal because the structural engineer will design the structure based on Fy of steel (36ksi or 50ksi)