What is the minimum yield strength of S355 I-beams per EN 10025-2?

EN 10025-2 specifies a minimum yield strength of 355 MPa for S355 I-beams (thickness ≤16mm). For thicker sections (16-40mm), the yield strength decreases slightly to 345 MPa due to reduced cooling rates during rolling, which coarsen grain structure. This high strength allows lighter designs in construction-e.g., a 10m span bridge using S355 I-beams requires 20% less material than S235. The yield strength is verified via tensile tests on samples cut from the flange, ensuring the critical load-bearing area meets standards. S355's strength-to-weight ratio makes it ideal for high-rise buildings and heavy machinery frames.