Steel trusses originate from classical steel and hall construction and are also used in large buildings like aircraft hangars due to their impressive spans and load-bearing capacity. A lattice structure composed of standard rolled profiles allows for spans up to 45 meters without the need for supports. A steel truss is best applied where a large span must be bridged while simultaneously creating slim and tall structures.
Adaptation to forces
Steel trusses consists of upper and lower flanges with intervening crossbars made from commercially available rolled profiles (such as square tubes, round tubes, IPE- or HE- profiles). Ideally, only the joints are subjected to tensile and compressive forces. For very large spans, welded profiles are often chosen for the upper and/or lower flanges due to their better adaptation to forces, instead of rolled profiles. A truss is only cost-effective if the joints are designed to be as simple as possible and the welds are not oversized. In most cases, rigid joints are chosen over hinges.
Structural form
In contrast to the traditional steel trusses, a Vierendeel truss consists of upper and lower girders with (exclusively) vertically welded uprights. This requires more material but offers larger openings in the framework.
Alternatives
Depending on the load and the required arch in large spans, it may be considered, due to mass distribution, to opt for a castellated or cellular beam. Welded plate girders with thin bodies often offer an economical alternative.