Which GB grade substitutes for the widely used European grade EN S355JR in I-beam applications?

The primary substitute for EN S355JR is GB Q355B (which superseded the old Q345B). Both have a minimum yield strength of 355 MPa for sections up to 16mm thick. S355JR, per EN 10025-2, mandates a Charpy impact energy of 27J at +20°C. Q355B has an identical impact requirement. This makes them highly interchangeable from a mechanical property standpoint. Chemically, both are high-strength low-alloy (HSLA) steels, achieving their strength through controlled levels of manganese and other micro-alloying elements. The production standards for the beams themselves, EN 10034 for dimensional tolerances and GB/T 11263 for hot-rolled H and I-sections, are also harmonized to a great extent, ensuring similar geometric profiles. Therefore, Q355B is a robust and standard substitute for S355JR in structural frames, bridges, and industrial buildings.