Types Of Long Span Trusses
A roof truss stands for a structure with one or numerous triangular units which comprise of straight slender members with their ends attached through nodes. Trusses belong to frame works in which the members susceptible to essentially axial forced caused by externally applied load. Bending causes compression in the top chords (or horizontal members), tension in the bottom chords as well as either tension or compression in the vertical and diagonal members.
Pitched Roof Truss A pitch roof truss contains a bottom chord having two inclined top chord attached with guest plates or panels. Additional supports are also provided in the form of struts according to the need. These trusses contain a larger depth at mid-span.
Parallel Chord Truss Parallel Chord Truss contains a bottom chord and a top chord that run parallel to each other. Additional supports are also provided in the form of struts according to need.
King Post Truss It belongs to a central vertical post that is utilized in architectural or bridge design. It functions in tension to give support to a beam underneath from a truss apex above.
Queen Post Truss A queen post truss bridge comprises of two uprights which are arranged about one-third of the way from each end of the truss. These are attached across the top with a beam and apply a diagonal brace among the exterior edges.
Pratt Truss Under this type of truss, the web members are placed in such a manner so that against gravity load, the longer diagonal members remain under tension and the shorter vertical members undergo compression. It is suitable for spans that vary among 6-10m.
Howe Truss It is mostly found in light roofing in order that the longer diagonals undergo tension under reversal of stresses caused by wind load. It is suitable for spans that vary among 6-30m.
Fink Truss Fink truss is ideal for longer spans with high pitch roof, as the web members in such truss are subdivided to acquire shorter members.
Fan Truss It is suitable while the rafter members of the roof truss are sub-divided into odd number of panels.
Scissor Truss It is mostly used in cathedrals. The benefit is that the ceiling gets vaulted and lots of spaces in the attic are created.
Warren Girder Parallel chord trusses apply webs of the similar lengths and consequently minimize fabrication costs for very long spans. Modified warren with extra verticals are applied to curtail the unsupported length of compression chord members.
Lattice Girder It is generally formed with a combination of structural sections which are attached diagonal lacing. This member is known as laced strut or laced tie.
North Light Truss This type of truss facilitates north light within the structure with skylights or openings.
Vierendeel Truss The vierendeel truss refers to a structure where the members create rectangular openings without being triangulated. It is a frame having fixed joints to transmit and withstand bending moments.
K-type Truss K patterns for web can be used for very deep and very shallow trusses to obtain exact inclination of the web members.
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