I-section steel, whether ordinary or light, has relatively high and narrow cross-section size, so the moment of inertia of the two main axes of the cross-section is quite different. Therefore, I-section steel can only be used directly for members bent in the web plane or for members subjected to lattice loads. Axial compression members or those that are perpendicular to the web plane and bending are not suitable for use, which limits their application. I-beam is widely used in construction or other metal structures.