The dimensional series for hot-rolled Q355B I-beams are specified in GB/T 706-2016, which categorizes them into two main types and several series. The standard provides designations and nominal dimensions for a wide range of sections.
1. H-beams (Parallel Flange Beams): These have nearly parallel flange surfaces and a constant web thickness. They are subdivided into three series based on their width-to-height proportions and intended use:
* HW (H-Wide Flange): Sections with height and flange width approximately equal. They are used as columns or heavy beam-columns. Example: HW 200x200.
* HM (H-Middle Flange): Sections where the height is roughly 1.5 times the flange width. They offer a good balance for both bending and axial load. Example: HM 350x250.
* HN (H-Narrow Flange): Sections where the height is significantly greater than the flange width. They are optimized for beams where bending resistance about the major axis is primary. Example: HN 400x200.
2. I-beams (Tapered Flange Beams): These are the traditional I-sections with inner flange surfaces tapered at a slope (typically 1:6). They are designated by their height in centimeters. Example: I 25a (where 'a' denotes a lighter series for that height compared to 'b' or 'c'). For each specific designation (e.g., HN 400x200x8x13), the standard lists the exact nominal dimensions: Height (h), Flange Width (b), Web Thickness (t1), Flange Thickness (t2), Fillet Radius (r), and Sectional Area. It also provides theoretical weight per meter, moments of inertia (Ix, Iy), section moduli (Wx, Wy), and radii of gyration (ix, iy) for design calculations. Tolerances for height, width, thickness, camber, and twist are also specified to ensure fit for purpose.