Whether the I-beam is ordinary or light, due to the relatively high and narrow section size, the moment of inertia of the two main axes of the section is quite different, so it can only be directly used for bending in the plane of its web. member or form it into a lattice-type force-bearing member.

In the structural design, the selection of I-beam should be based on its mechanical properties, chemical properties, weldability, structural size, etc. to select a reasonable I-beam for use.

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

Its specifications are expressed by height × leg thickness × waist thickness, and the main dimensions of the specifications can also be expressed by numbers. For example, No. 18 I-beam means I-beam with a height of 18cm. If the I-beams are of the same height, the angle code a or b or c can be added after the number, such as 36a, 36b, 36c, etc.