◆Regardless of whether it's a standard or lightweight I-beam, due to the relatively high and narrow cross-sectional dimensions, the inertial moments of the two main flanges differ significantly. Therefore, it is generally only suitable for components that bend within the plane of the web or for components that form a truss-like structural system. It is not advisable for components under axial compression or for those with bending perpendicular to the web plane, which greatly limits its scope of application.

H-beams are part of the economic section profiles category, which also includes cold-formed thin-walled steel sections and corrugated steel plates, etc. Due to their rational cross-sectional shape, they allow steel to be utilized more effectively, enhancing load-bearing capacity. Unlike standard I-beams, the flanges of H-beams are widened, and their inner and outer surfaces are typically parallel, facilitating the use of high-strength bolts and other components for connections. Their dimensions are well-structured in a series, with a complete range of models, making them convenient for design selection.

◆The flanges of H-shaped steel are all of equal thickness, featuring rolled cross-sections as well as composite sections composed of three plates welded together. I-shaped steel is exclusively rolled, and due to poor production techniques, the inner edge of the flange has a 1:10 slope. The rolling process for H-shaped steel differs from that of ordinary I-shaped steel, which uses only a set of horizontal rolling rolls. Since the flanges of H-shaped steel are wider and have minimal slope (or no slope at all), an additional set of vertical rolling rolls is required for rolling, making the rolling process and equipment more complex than those of standard rolling machines. The maximum height of rolled H-shaped steel that can be produced domestically is 800mm, with any taller dimensions requiring a welded composite section. China's national standard for hot-rolled H-shaped steel (GB/T11263-1998) categorizes H-shaped steel into narrow flange, wide flange, and steel pile types, with the designations hz, hk, and hu, respectively. Narrow flange H-shaped steel is suitable for beams or bending members, while wide flange H-shaped steel and H-shaped steel piles are used for axially compressed members or bending members. Compared to H-shaped steel, I-shaped steel is inferior in terms of w, ix, and iy, under the same weight condition.