Large spans

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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.

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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.

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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.

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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.