I-beams are mainly divided into ordinary I-beams, light-duty I-beams and wide-flange I-beams. According to the height ratio of the flange to the web,

 it is divided into wide, medium and narrow wide flange I-beams. The first two production specifications are 10-60, that is,

 the corresponding height is 10 cm-60 cm. At the same height, the lightweight I-beam has narrow flanges, thin webs and light weight. 

The wide-flange I-beam is also called H-beam, and its cross-section is characterized by parallel legs and no slope on the inner side of the legs.

 It belongs to economic section steel, which is rolled on a four-high universal rolling mill, so it is also called "universal I-beam". 

Ordinary I-beams and light-duty I-beams have become national standards.

Regardless of whether the I-shaped steel is ordinary or light, because the cross-section size is relatively high and narrow,

 the moment of inertia of the two main axes of the cross-section is quite different, so it can only be directly used for bending in the plane of its web. 

Components or form them into lattice-type force-bearing components. It is not suitable to use axial compression members

 or members that are perpendicular to the plane of the web and bend, which makes the application range very limited.

 I-beams are widely used in construction or other metal structures.

Ordinary I-beams and light-duty I-beams have relatively high and narrow cross-sections, so the moments of inertia of the two main

 axes of the cross-sections are quite different, which limits their application range. The use of I-beam should be selected according to the requirements of the design drawings.

The specifications are expressed in terms of height × leg thickness × waist thickness, and the number can 

also be used to indicate the main size of the specification. For example, No. 18 I-beam means an I-beam with a height of 18 cm.

 For I-beams of the same height, they can be indicated by adding angle codes a, b, or c after the number, such as 36a, 36b, 

36c, and so on. It is divided into ordinary I-beam, light I-beam and wide flange I-beam. According to the height ratio 

of the flange to the web, it is divided into wide, medium and narrow wide flange I-beams. 

The specifications produced by the first two are 10-60, that is, the corresponding height is 10 cm-60 cm