Steel Buildings in Europe

Part 1: Architect’s Guide 1 - 22 Fink or Polonçeau truss (small span) Fink or Polonçeau truss (large span) Belgian truss English truss Mansard truss Figure 3.16 Types of pitched roof truss Flat trusses Flat trusses are used mainly in rigid frames (see Section 0 for a more comprehensive description) but they are also employed in pinned frames – an example is shown in Figure 3.17. Figure 3.17 Flat truss in pinned frame building Trusses typically have a greater depth than single beams or plate girders. The deflection of a truss is modest, and can be controlled, making trusses especially suitable when significant loads have to be supported from the roof structure, or when a flat (or nearly flat) roof is to be provided. The larger depth of the trusses increases the dimensions of the façade, but also provides space for services to be placed in the roof structure instead of below. The weight of a trussed roof structure per unit area of roof in general is less than that of single beam girders, but the fabrication costs are higher. Trusses