Steel i beam, whether ordinary or light, has a relatively high and narrow cross-section size, so the moment of inertia of the two main axes of the cross-section is quite different, so it can only be directly used for members bent in the plane of its web plate or composed of latticed members. It is not suitable for axial compression members or members that are bent in the plane perpendicular to the web, which limits their application.
steel i beam are mainly divided into ordinary steel i beam, light steel i beam and wide flange steel i beam. steel i beam with wide flanges, medium flanges and narrow flanges are divided according to the height ratio of flanges to webs. The specifications of the former two are 10-60, that is, the corresponding height is 10 cm—60 cm. At the same height, light steel i beam has narrow flange, thin web and light weight. steel i beam with wide flange, also known as steel H beam, is characterized by parallel legs and no inclination inside the legs. It belongs to economic section steel and is rolled on a four-high universal rolling mill, so it is also called "universal steel i beam".