American W-shapes (ASTM A6) are functional equivalents to China's GB HM (Medium Flange) H-beams for medium-load applications (e.g., building columns, secondary bridge girders), with key comparisons and adjustments:
Dimensional Alignment:
W10x49 (ASTM): Depth 10.09 inches (≈256 mm), flange width 8.00 inches (≈203 mm), web thickness 0.345 inches (≈8.8 mm), weight 49 lbs/ft (≈73.1 kg/m).
HM 250x118 (GB): Depth 250 mm, flange width 118 mm, web thickness 6.5 mm, weight 31.9 kg/m.W10x49's wider flanges (203 mm vs. 118 mm) and higher weight (73.1 kg/m vs. 31.9 kg/m) provide greater load capacity, making it suitable for HM applications requiring enhanced stability.
Load Capacity Adjustments: When substituting W-shapes for HM beams, engineers use section modulus and moment of inertia values from ASTM and GB standards to ensure equivalent performance. For example, a HM 250x118 Q355B beam has a section modulus of ≈230 cm³ (≈14 in³), while a W10x49 A992 beam has ≈49.1 in³-three times higher. To match load capacity, a smaller W-shape (e.g., W8x31, ≈14.9 in³) can be used, reducing material cost while maintaining performance.
Connection Design: HM beams use narrow-flange connections (e.g., single-bolt brackets), while W-shapes require wider brackets to accommodate their flanges. For example, a bracket designed for HM 250x118's 118 mm flange width may need to be modified to 200 mm to fit W8x31's 6.53 inch (≈166 mm) flange. This adjustment is straightforward using standard steel fabrication details (e.g., AISC Steel Construction Manual, GB 51022-2015).
By selecting appropriately sized W-shapes and adjusting connections, American H-beams can reliably substitute GB HM beams in medium-load projects.