Statics: Effect of Different Cross Sections

I section members with holes (cellular beams and columns)

Fig. 3-9: Cellular columns                                          Fig. 3-10: Cellular beams

As the material close to the neutral axis of a section does not contribute efficiently to the second moment of area and hence the stiffness of a member, this material can be removed making the member lighter and saving material. It is quite common to see I section beams and columns with holes along their neutral axes.

Fig. 3-9 shows a car showroom in which the external columns support the roof. The external columns are all I sections with material around their neutral axes removed to create a lighter structure of more elegant appearance. Cellular columns are most effective in cases where axial loads are small. Fig. 3-10 shows cellular beams used in an airport terminal.