Channel steel (U-shaped steel) dimensions vary by regional standards:
China (GB/T 707): Defines channels by height (h), leg width (b), and web thickness (d), e.g.:
No. 5: h=50mm, b=37mm, d=4.5mm
No. 20: h=200mm, b=73mm, d=7mm
Classifications: Light (Y) and ordinary (I), with inner arc radii specified for leg edges.
US (ASTM A36/A572): C-shapes (e.g., C10×20, height 10in, weight 20lbs/ft) and MC-shapes (modified channels with wider flanges).
Europe (EN 10027/EN 10279): UPN (narrow flanges) and UPE (wide flanges), e.g., UPN100: h=100mm, b=50mm, d=5mm.
Japan (JIS G3192): SHF series (e.g., SHF100: h=100mm, b=50mm, d=5mm), optimized for seismic resistance.
Key note: Chinese channels prioritize cost efficiency for infrastructure, while US MC-shapes suit heavy machinery due to wider flanges.