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A king post (or king-post or kingpost) is a central vertical post used in architectural or bridge designs, working in tension to support a beam below from a truss apex above (whereas a crown post, though visually similar, supports items above from the beam below).
In aircraft design a strut called a king post acts in compression, similarly to an architectural crown post. Usage in mechanical plant and marine engineering differs again, as noted below.
A king post extends vertically from a crossbeam (the tie beam) to the apex of a triangular
The king post truss is used for simple roof trusses and short-span bridges. It is the simplest form of truss in that it is constructed of the fewest truss members (individual lengths of wood or metal). The truss consists of two diagonal members that meet at the apex of the truss, one horizontal beam that serves to tie the bottom end of the diagonals together, and the king post which connects the apex to the horizontal beam below. For a roof truss, the diagonal members are called rafters, and the horizontal member may serve as a ceiling joist. A bridge would require two king post trusses with the driving surface between them. A roof usually uses many side-by-side trusses depending on the size of the structure.
Pont-y-Cafnau, the world's first iron railway bridge, is of the king post type.
A king post (or king-post or kingpost) is a central vertical post used in architectural or bridge designs, working in tension to support a beam below from a truss apex above (whereas a crown post, though visually similar, supports items above from the beam below).
In aircraft design a strut called a king post acts in compression, similarly to an architectural crown post. Usage in mechanical plant and marine engineering differs again, as noted below.
Architecture
A king post extends vertically from a crossbeam (the tie beam) to the apex of a triangular truss
A truss is an assembly of ''members'' such as beams, connected by ''nodes'', that creates a rigid structure.
In engineering, a truss is a structure that "consists of two-force members only, where the members are organized so that the assembla ...
. The king post, itself in tension, connects the apex of the truss with its base, holding up the tie beam (also in tension) at the base of the truss. The post can be replaced with an iron rod called a king rod (or king bolt) and thus a king rod truss. The king post truss is also called a "Latin truss".
In traditional timber framing, a crown post looks similar to a king post, but it is very different structurally: whereas the king post is in tension, usually supporting the tie beam as a truss, the crown post is supported by the tie beam and is in compression. The crown post rises to a crown plate immediately below and supporting collar beams, it does not rise to the apex like a king post. Historically a crown post was called a king post in England but this usage is obsolete.
An alternative truss construction uses two queen posts (or queen-posts). These vertical posts, positioned along the base of the truss, are supported by the sloping sides of the truss, rather than reaching its apex. A development adds a collar beam above the queen posts, which are then termed queen struts. A section of the tie beam between the queen posts may be removed to create a hammerbeam roof.
King post truss
The king post truss is used for simple roof trusses and short-span bridges. It is the simplest form of truss in that it is constructed of the fewest truss members (individual lengths of wood or metal). The truss consists of two diagonal members that meet at the apex of the truss, one horizontal beam that serves to tie the bottom end of the diagonals together, and the king post which connects the apex to the horizontal beam below. For a roof truss, the diagonal members are called rafters, and the horizontal member may serve as a ceiling joist. A bridge would require two king post trusses with the driving surface between them. A roof usually uses many side-by-side trusses depending on the size of the structure.
Pont-y-Cafnau, the world's first iron railway bridge, is of the king post type.
History
King posts were used in timber-framed roof construction in Roman buildings, and inmedieval architecture
Medieval architecture is architecture common in the Middle Ages, and includes religious, civil, and military buildings. Styles include pre-Romanesque, Romanesque, and Gothic. While most of the surviving medieval architecture is to be seen in ...
in buildings such as parish church
A parish church (or parochial church) in Christianity is the church which acts as the religious centre of a parish. In many parts of the world, especially in rural areas, the parish church may play a significant role in community activitie ...
es and tithe barn
A tithe barn was a type of barn used in much of northern Europe in the Middle Ages for storing rents and tithes. Farmers were required to give one-tenth of their produce to the established church. Tithe barns were usually associated with the ...
s. The oldest surviving roof truss in the world is a king post truss in Saint Catherine's Monastery, Egypt, built between 548 and 565.
King posts also appear in Gothic Revival architecture
Gothic Revival (also referred to as Victorian Gothic, neo-Gothic, or Gothick) is an architectural movement that began in the late 1740s in England. The movement gained momentum and expanded in the first half of the 19th century, as increasingly ...
, Queen Anne style architecture and occasionally in modern construction. King post trusses are also used as a structural element in wood and metal bridges.
A painting by Karl Blechen circa 1833 illustrating construction of the second Devil's Bridge (''Teufelsbrücke'') in the Schöllenen Gorge shows multiple king posts suspended from the apex of the falsework upon which the masonry arch has been laid. In this example, beams in compression are supported by each king post several feet below the apex, and the bottom of the king posts can clearly be seen to be unsupported.
Norman truss
Architectural historians in the French colonial cities St Louis,Missouri
Missouri is a U.S. state, state in the Midwestern United States, Midwestern region of the United States. Ranking List of U.S. states and territories by area, 21st in land area, it is bordered by eight states (tied for the most with Tennessee ...
and New Orleans
New Orleans ( , ,New Orleans
On a cargo ship or oiler a king post is an upright with cargo-handling or fueling rig devices attached to it. On a cargo vessel king posts are designed for handling cargo, and so are located at the forward or after end of a hatch. For an oiler they are located over the fuel transfer lines.
Bridge BasicsTimber roofsCrown post roofsKing and Queen post roofs on the former mansion at Parlington, near Aberford in Yorkshire, England
(archived) Architectural elements Structural engineering Trusses Timber framing Truss bridges by type
Louisiana
Louisiana , group=pronunciation (French: ''La Louisiane'') is a U.S. state, state in the Deep South and South Central United States, South Central regions of the United States. It is the List of U.S. states and territories by area, 20th-smal ...
use the term "Norman roof" to refer to a steeply pitched roof; it is supported by what they call a "Norman truss" which is similar to a king post truss. This is a through-purlin truss consisting of a tie beam and paired truss blades, with a central king post to support the roof ridge. The name derives from a belief that this system of construction was introduced to North America by settlers from Normandy
Normandy (; french: link=no, Normandie ; nrf, Normaundie, Nouormandie ; from Old French , plural of ''Normant'', originally from the word for "northman" in several Scandinavian languages) is a geographical and cultural region in Northwestern ...
in northern France, but it is really a misnomer as the system was more widely used than that. The difference between a Norman truss and a king post truss is the tie beam in a Norman truss is technically a collar beam (a beam between the rafters above the rafter feet) where the king post truss the rafters land on top of a tie beam.
Aviation
King posts are also used in the construction of somewire-braced
In aeronautics, bracing comprises additional structural members which stiffen the functional airframe to give it rigidity and strength under load. Bracing may be applied both internally and externally, and may take the form of strut, which act in ...
aircraft, where a king post supports the top cables or "ground wires" supporting the wing. Only on the ground are these wires from the kingpost in tension, while in the air under positive g flight they are unloaded.
Mechanical plant
The very robust hinge connecting the boom to the chassis in a backhoe, similar in function and appearance to a large automotivekingpin
Kingpin or king pin may refer to:
Vehicular part
* Kingpin (automotive part), the pivot in the steering mechanism
** The central bolt of a skateboard, axle assembly ("truck"), around which the rest of the mechanism can flex, allowing the rider ...
, is called a king post.
Marine engineering
On a cargo ship or oiler a king post is an upright with cargo-handling or fueling rig devices attached to it. On a cargo vessel king posts are designed for handling cargo, and so are located at the forward or after end of a hatch. For an oiler they are located over the fuel transfer lines.
See also
* Strut * Cabane strut *Queen post
A queen post is a tension member in a truss that can span longer openings than a king post truss. A king post uses one central supporting post, whereas the queen post truss uses two. Even though it is a tension member, rather than a compression m ...
*Timber roof truss
A timber roof truss is a structural framework of timbers designed to bridge the space above a room and to provide support for a roof. Trusses usually occur at regular intervals, linked by longitudinal timbers such as purlins. The space between ea ...
References
Notes Bibliography * *{{cite book , last=Wood , first=De Volson , title=Treatise on the Theory of the Construction of Bridges and Roofs , url=https://archive.org/details/treatiseontheor03woodgoog , year=1883 , publisher=J. Wiley & SonsExternal links
Bridge Basics
(archived) Architectural elements Structural engineering Trusses Timber framing Truss bridges by type