Truss

Although this rigorous definition allows the members to have any shape connected in any stable configuration, architectural trusses typically comprise five or more triangular units constructed with straight members whose ends are connected at joints referred to as nodes.

[4] Truss derives from the Old French word trousse, from around 1200 AD, which means "collection of things bound together".

[5][6] The term truss has often been used to describe any assembly of members such as a cruck frame[7][8] or a couple of rafters.

[9][10] A truss consists of typically (but not necessarily) straight members connected at joints, traditionally termed panel points.

This type of truss is seen in a framed roof consisting of rafters and a ceiling joist,[13] and in other mechanical structures such as bicycles and aircraft.

[16] The depth of a truss, or the height between the upper and lower chords, is what makes it an efficient structural form.

A solid girder or beam of equal strength would have substantial weight and material cost as compared to a truss.

A tetrahedron shape is the simplest space truss, consisting of six members that meet at four joints.

Therefore, for given planar truss with a fixed depth, the Pratt configuration is usually the most efficient under static, vertical loading.

The Wright Flyer used a Pratt truss in its wing construction, as the minimization of compression member lengths allowed for lower aerodynamic drag.

His design, patented in 1820 and 1835, uses easy-to-handle planks arranged diagonally with short spaces in between them, to form a lattice.

Thousands of bowstring trusses were used during World War II for holding up the curved roofs of aircraft hangars and other military buildings.

The primary difference is the horizontal extension at the centre which relies on beam action to provide mechanical stability.

It is rarely used for bridges because of higher costs compared to a triangulated truss, but in buildings it has the advantage that a large amount of the exterior envelope remains unobstructed and it can therefore be used for windows and door openings.

Trusses that are supported at more than two positions are said to be statically indeterminate, and the application of Newton's Laws alone is not sufficient to determine the member forces.

While the relation (a) is necessary, it is not sufficient for stability, which also depends on the truss geometry, support conditions and the load carrying capacity of the members.

Because the forces in each of its two main girders are essentially planar, a truss is usually modeled as a two-dimensional plane frame.

The analysis of trusses often assumes that loads are applied to joints only and not at intermediate points along the members.

Provided that the members are long and slender, the moments transmitted through the joints are negligible, and the junctions can be treated as "hinges" or "pin-joints".

Trusses are physically stronger than other ways of arranging structural elements, because nearly every material can resist a much larger load in tension or compression than in shear, bending, torsion, or other kinds of force.

Individually, they are also in tension and compression, the exact arrangement of forces is depending on the type of truss and again on the direction of bending.

In the adjacent picture, the top chord is prevented from buckling by the presence of bracing and by the stiffness of the web members.

In other cases the appearance of the structure may take on greater importance and so influence the design decisions beyond mere matters of economics.

Wood posts enable the fabrication of strong, direct, yet inexpensive connections between large trusses and walls.

Solid-sawn timber and glulam posts are generally notched to form a truss bearing surface.

Truss bridge for a single-track railway, converted to pedestrian use and pipeline support. In this example the truss is a group of triangular units supporting the bridge.
Typical detail of a steel truss, which is considered as a revolute joint
Historical detail of a steel truss with an actual revolute joint
An Egyptian ship with a rope truss, the oldest known use of trusses. Trusses did not come into common use until the Roman era.
Planar roof trusses
The roof trusses of the Basilica di Santa Croce in Florence
Roof truss
A large timber Howe truss in a commercial building
Tempe Salt River Southern Pacific Railroad bridge
Lattice Truss
Lattice Truss
A bowstring truss is used on the oldest metal bridge in Virginia
King Post Truss
King Post Truss
Queen Post Truss
Queen Post Truss
A South Australian Railways passenger car built in 1918 with queen post trusses. The queen posts are the two vertical components; the short horizontal tube at the mid-point of the truss rod is the turnbuckle, which is adjusted by rotating to achieve the desired support of the car's frame.
The Waterville Bridge in Swatara State Park in Pennsylvania is a lenticular truss
A Vierendeel bridge , which lacks diagonal elements in the primary structure
Cosmonaut Alexander Serebrov sets up an integrated truss structure " Rapana " at Mir space station , September 16, 1993
Cremona diagram for a plane truss
Truss sections stabilize this building under construction in Shanghai and will house mechanical floors
A type of truss used in roofing