Fabricated profiles can come in many forms, but usually they are limited to Plate Girders, Box Girders and castellated or Cellular profiles.
A plate girder (or built-up section) is typically formed into an I or H profile from separate web and flange plates. The plates may be either bolted, riveted, or welded together to form the profile, but today, welding is the de-facto standard.
They may be configured as columns or beams which carry heavy loads that cannot be achieved economically by standard hot-rolled sections.
Few workshops today fabricate their own plate girders, preferring instead to obtain them from merchants or suppliers equipped with automated cutting and welding facilities enabling them to make them economically to a high standard.
The alternatives to Plate girders include: Truss or Lattice Girders or a Compound Girder.
A box girder is a square, rectangular or trapezoidal fabricated hollow section which may be either Open or Closed Cell.
They are rarely used in buildings due to cost and erection difficulties, especially in confined spaces. Instead they are more commonly found in Bridges where their ability to carry large loads over long spans with high torsional stiffness is of particular benefit.
A castellated beam is usually formed from a standard hot-rolled I or H section. The castellated pattern is cut symmetrically into the web of the beam, which is them separated and shifted a half pitch in relation to one another and them welded together. The result is a beam which is deeper by approximately 1.5 than the original while maintaining the same weight.
The castellated beam can be made even deeper by welding extension plates between the ‘teeth’
For extra long spans a Castellated beam can be cut from a Welded Plate Girder - In such cases the castellation's are cut directly into the web of the girder without any need to cut and re-align
They are employed mainly as wide-span secondary beams – the castellation’s allow for the passage of pipes and/or electrical services.
Cellular beams are in many ways similar to Castellated beams with the obvious difference being the fact that the openings are circular.
As with Castellated Beams, they are formed by symmetrically cutting the cellular pattern in the beam which is them separated and shifted by a half pitch relative to one another and welded together to form the cellular pattern.
The geometry of Cellular Beams can be more easily modified than Castellated Beams allowing for greater design versatility making them popular with architects and engineers seeking and enhanced aesthetic appeal