Steel Buildings in Europe

Part 1: Architect’s Guide 1 - 20 Figure 3.13 Tapered plate girders Plate girders are likely to be more expensive than hot-rolled standard sections. Beams with web openings Because roof beams generally carry relatively light uniformly distributed loads, beam sections that span large distances can be created by fabricating sections with openings in the webs. Historically, the first beam of this type was the castellated beam, with hexagonal holes. Now beams with circular openings are commonly used. In both cases, the beam is fabricated from a rolled I section by cutting along the web, to a special profile, separating the two halves and then displacing one half relative to the other and welding them back together. This is illustrated in Figure 3.14. The major advantage of this type of beam is the weight reduction: approximately 30% less than a beam with a solid web of similar depth and bending resistance. An example of the use of beams with circular openings is shown in Figure 3.15. Beams with web openings are less suitable for heavy concentrated loads. The span/depth ratio is typically 30 for spans up to 50 m. Hexagonal holes Circular holes Figure 3.14 Fabrication of beams with web openings