Roof truss

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Roof trusses, Figs. 1 and 2 show roof structures without a chair structure. Overview from Meyers Konversationslexikon, 4th ed. 1885–90

The term roof structure is usually used to describe the entire structure of a roof structure , if it is composed of individual support members as a supporting structure and thereby forms a traditional roof shape . It is usually made of wood, in larger buildings it is also made of support members made of iron or reinforced concrete .

In contrast, a chair in the original and narrower sense is a partial structure of the roof structure that can be arranged in rafter and purlin roofs under the rafter layer. It supports the rafters or collar beams and serves to stiffen the roof. It is stable for itself and without the involvement of the rafters. The chair forms a longitudinal structure under the rafters, to which the roof trusses also belong on the purlin roof .

Word origin

The word has been used in German since the 16th century, the word component " chair " means "frame", especially one on which something else rests. In this respect, the roof truss is regarded as a “frame on which the roof cladding rests, is attached”, as a “[wood] structure supporting the roof cladding”.

construction

In the case of a wooden chair construction in a roof structure, the supports or stems are also referred to as chair posts or chair columns . Together with thresholds , frames and struts, a row of these forms a longitudinal structure parallel to the ridge, the chair wall . The threshold for distributing the load under chair posts is also called the chair threshold .

The bracing of the posts and purlins to the chair wall, which is often carried out with head straps , facilitates the erection of the roof structure and, together with wind panes, ensures the longitudinal bracing of the roof structure. The connection of the chair columns with the tension bars by struts serves to reinforce the chair transversely.

Standing chair

View a panoramic view of a historic roof structure in the library building of the Eberbach Monastery
as a spherical panorama

A standing chair is a chair with vertical pillars. If these are only arranged in the longitudinal axis under the ridge to support the ridge purlin or to support the collar beams in the middle, then we speak of a single standing chair , in a two-row position, a double or double standing chair . Combined constructions are also called multiple standing chairs .

A standing chair is the standard construction of the purlin roof as a gable roof if the central purlin cannot be supported on a central wall or on transverse and gable walls. A rafter and collar beam roof , on the other hand, can be erected without a chair in the case of small spans.

The collar beams of a larger collar beam roof are often supported at the connection points to the rafters by two chair purlins (also chair wall purlins or chair frames ). The purlins are supported by chair posts and form a double roof structure with vertical posts .

A hanging truss is created when the ceiling under the roof is suspended from the chair pillars, for example to create a large, column-free hall (figure roof trusses, Figs. 14 and 15). The loads from the ceiling and the supported roof structure are then transferred to the supports at the base of the rafters using struts and, if necessary, tension bars.

Historic collar beam roof with a reclining chair. The actual chair construction is shown in blue.

Lying chair

When the chair is lying down , the chair columns are inclined at an angle and are supported at the top on the tension bar . Their base points are usually on the ceiling joist just above the outer wall or another load-bearing wall. Reclining chairs can be arranged in purlin, rafter and collar beam roofs.

One advantage of this arrangement is that the column-free roof space can be used better. The lying chair also loads the underlying ceiling joists at the edge near the support and not in the center of the field. This ensures a lower bending moment . The reclining chair is therefore also used when large, column-free spaces are to be created on the floor below the beam position and the ceiling cannot be loaded by the roof structure, for example above the nave of a church.

Views

literature

Individual evidence

  1. ↑ For example, in Anton pitch and Karlheinz Hollinsky: Roof trusses , Vienna, 2005, Springer.
  2. ↑ Klaus Dierks (Ed.): Building construction , 2nd edition, Düsseldorf, 1990 p. 447.
  3. ↑ Composition based on Günther Wasmuth (ed.): Wasmuths Lexikon der Baukunst , Berlin, 1929–1932 (4 volumes), Lemma Dachstuhl
  4. ↑ a b sentence based on Kluge Etymological Dictionary of the German Language , 24th edition, 2002.
  5. ↑ according to Duden online at www.duden.de, Lemma Dachstuhl , accessed on December 12, 2008.
  6. ↑ a b sentence based on Hagen Prehl: Wooden roof structures , 2nd edition, Düsseldorf, 2001, Werner Verlag, p. 43.
  7. ↑ Composition based on Günther Wasmuth (ed.): Wasmuths Lexikon der Baukunst , Berlin, 1929–1932 (4 volumes), Lemma Stuhlwand .
  8. ^ A b c sentence after Hagen Prehl: Wooden roof structures , 2nd edition, Düsseldorf, 2001, Werner Verlag, p. 45.
  9. ^ Sentence after Günther Binding (Ed.): Specialized terminology for historical timber construction. Fachwerk - roof structure. 38. Publication by the Department of Architectural History of the Art History Institute of the University of Cologne. 2nd revised edition, Cologne 1990. p. 15.
  10. ^ Sentence after Günther Binding (Ed.): Specialized terminology for historical timber construction. Fachwerk - roof structure. 38. Publication by the Department of Architectural History of the Art History Institute of the University of Cologne. 2nd revised edition, Cologne 1990. Graphic p. 14.
  11. ↑ Composition according to Günther Wasmuth (ed.): Wasmuths Lexikon der Baukunst , Berlin, 1929–1932 (4 volumes), Lemma Stuhlwandpfette . "... the 16/18 to 18/20 thick purlins, which are used to support collar beams over 3.5 to 4 m long ..."

Web links

Commons : Roof Truss  - Collection of images, videos and audio files
Wiktionary: Roof truss  - explanations of meanings, word origins, synonyms, translations