1.Whether the I-shaped steel is ordinary or light, because the cross-sectional size is relatively high and narrow, the two main sleeves of the moment of inertia cross-section are greatly different, so it usually can only directly use the internal bending components of the aircraft on the network or It can be made into lattice components. It is not suitable for axial compression members or members perpendicular to the web or bending members, so that its application range is very limited.

2. H-shaped steel is an economical cutting profile (others include cold-formed thin-walled steel and special-shaped steel plates, etc.). Due to the reasonable cross-sectional shape, the steel can be made more efficient and the cutting ability can be improved. Different from the general i-shaped steel, the flange of the h-shaped steel is widened, and the inner and outer surfaces are usually parallel, which is convenient for the connection of high-strength bolts and other parts. Its size constitutes a reasonable series, complete models, easy to design and select. (Except for I-beams of lifting beams)

3. The flanges of H-shaped steel are of equal thickness, with rolling sections and combined sections welded by three steel plates. I-beams are all rolled sections. Due to poor production technology, the slope of the flange inner edge is 1:10. The rolling of h-beam is different from ordinary I-beam. Only one set of transverse coils is used. Because the flange is wide and has no slope (or the slope is small), it is necessary to add a set of vertical rolls for simultaneous rolling. The rolling process and equipment are more complicated than ordinary rolling mills. The rolling height of h-shaped steel that can be produced in China is 800mm, which exceeds the welded composite section.