I-beams, also known as Universal beams, are long strips of steel with I-shaped sections. I - beams are divided into ordinary I - beams and light I - beams. It is a section steel with the shape of an I-beam.

Whether the I-section steel is ordinary or light, because the section size is relatively high and narrow, the inertia moment of the two main spindles of the section is very different, so it can only be directly used in the web plane bending members or it can be composed of lattice stressed members. It is not suitable for the axial compression member or the bending member perpendicular to the web plane, which makes its application scope has a great limitation. I-beams are widely used in buildings and other metal structures. 

Ordinary I-beam and light I-beam, due to the relatively high and narrow section size, the moment of inertia of the two main axes of the section is quite different, which makes it have a great limitation in the application range. The use of I-beam should be selected according to the requirements of the design drawings. 

The selection of I-beam in the structural design should be based on its mechanical properties, chemical properties, weldable properties, structural size and other reasonable selection of I-beam for use.