Types of Steel Trusses

A truss is a structural frame based on the geometric rigidity and stability of the triangle, which more effectively distributes tension and compression than other shapes. Trusses were originally developed by civil engineers and are routinely found in bridges and roofs where supporting great deals of weight is essential. There are, however, numerous types of trusses that have been developed over time to more aptly address specific architectural obstacles and concerns.

Pitched Truss

This truss, also known as a common truss, is characterized by triangular supports inside a larger triangular master frame. It is most often used in roof construction. The spacing and span of the supports can vary, creating a multitude of web configurations.

Parallel Chord Truss

This truss, also called a flat truss, is named for the parallel chords at the top and bottom of the frame that hold the triangular-shaped supports. It is most often used for floor construction.

Truncated Truss

This type of truss is a combination of a pitched truss and parallel chord truss, and is most often used in hip and pyramid roof construction where all sides slope downward toward the walls.

Bow String Roof Truss

With a top chord arched like a bow, this truss is most commonly found in warehouses, airplane hangars, and other large, open buildings.

King Post Truss

This is considered one of the simplest types of trusses to implement, consisting of only two angled supports that lean against a common, vertical center support. This is useful only for very short distances.

Pratt Truss

First patented in 1844 by two Boston railway engineers, this variation on the parallel chord truss interweaves angled supports with vertical beams, which more adequately respond to compression and tension than other types of trusses.

Town's Lattice Truss

Patented in 1820 and 1835 by an American architect, this truss is a latticework of angled supports forming X patterns with very small spaces between them. It was originally designed as an alternative to heavy timber bridges.

Vierendeel Truss

In an unusual departure from standard triangular supports, this truss uses only vertical supports that form rectangular openings and has fixed joints that can transfer and resist bending movements extremely well.

Lenticular Truss

First patented in 1878, this truss has both the bottom and top chords arched to form a lens shape. It can most commonly be found on American bridges.

Brown Truss

Originally patented in 1857, this truss is comprised of only wide, crisscrossing diagonal supports that form X shapes and have no vertical braces. It is most often found in covered bridges.

K Truss

This truss is named for the K shape that is created in each panel by two angled supports that meet in the center of a vertical support.

Queen Post Truss

This type of truss consists of two vertical supports connected by a horizontal support, with an angled support on either side of the verticals. It was created as an alternative to the king post truss but is similarly used for short distances only.

Keywords: types of trusses, bridge trusses, roof trusses, truss designs

About this Author

Mark Heidelberger has been writing for more than 17 years, with recent articles appearing on websites such as eHow, Trails and GolfLink. He has also written, rewritten, and developed dozens of feature film screenplays and manages a number of film and television writers. He holds a master's degree from UCLA in film and television producing.

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