Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)


Civil Engineering


In recent years plastic analysis has been widely used in structural design throughout the United States. It is based on the maximum load-carrying capacity of the structure. It offers a more realistic design approach than the conventional elastic methods, where the true factor of safety against ultimate strength can and does vary significantly from one structure to another.

The main objective of this study is to determine the maximum load-carrying capacity of steel I-beams with hexagonal web cutouts. When the cutouts are arranged as shown in Figure 1-a, the beam presents an appearance exactly as does a castellated beam. A word relative to castellated beams may be appropriate here, however. A castellated beam consists of two halves of ro4led-steel shapes joined by welding after the web has been cut in a zig zag line, thus producing a beam with increased depth and hexagonal holes in the web as shown in Figure 1-b. The load carrying-capacity and stiffness of this beam then become greater than the original unexpanded shape. The reduction in beam weight has a chain effect on savings throughout the structure. The analyses and conclusions in this study are applicable to castellated beams.

Library of Congress Subject Headings

Strength of materials



Number of Pages



South Dakota State University