Inverted king post trusses are made of steel bars and cables used to reduce bending, deformation, and a trusses’ height. In other words, they are a collection of continuous beams (steel or wood) and steel cables that are positioned under the beam, supported by an upright king post. Although slender, they are suited for large spans and have small sections.
These posts are responsible for connecting beams, which in turn behave as continuous beams, reducing the span and, consequently, requiring a smaller section. They are tied by steel cables, which work under tension and support the system. Compared to a traditional beam, this model absorbs the forces and intrinsic efforts produced by the application of loads more efficiently. Commonly used in buildings where there is a need to free internal space and avoid pillars, they are often used in stadiums, bridges, and roofs with large spans.
Grid House by FGMF Arquitetos is a residential example of its use. Built in 2017 on uneven ground in Mantiqueira Sierra, Sao Paulo, it makes use of a rigid structural wooden grid of 5.5 meters x 5.5 meters. “To avoid an excessive number of pillars in the 2,000 square-meter buildings’ projection, we used inverted king post trusses (11 meters in length) every two modules made of corten steel” [1].
Another work which makes use of the system is Eucalyptus House by Andre Eisenlohr. Designed for a steep slope and positioned parallel to the gradient, the house is situated in a forest reserve in Campos do Jordão. Prefabricated systems were chosen for fast construction and low environmental impact. In this work, the roof’s main beams are made of inverted king post trusses to avoid a central pillar, freeing space and guaranteeing they won’t suffer deformations” [2].
An example of its use in a large scale building is Sebrae Headquarters in Brasilia by gruposp and Luciano Margotto. The structure mixes concrete and steel. The courtyard has a large span roof made of two inverted king post trusses of 3.60 meters in height and 36 meters in length.
Because of their visual lightness and great structural characteristics, the inverted king post trusses are a very interesting solution for several situations.
Notes:
[1] ArchDaily Brasil.
[2] ArchDaily Brasil.
References:
Eucalyptus House / Andre Eisenlohr. Retrieved from: ArchDaily. Retrieved: October 28, 2018.
Grid House / FGMF Arquitetos. Retrieved from: ArchDaily. Retrieved: October 28, 2018.
SEBRAE headquarters/ gruposp + Luciano Margotto. Retrieved from: ArchDaily. Retrieved: October 28, 2018.
Portal Metálica. Steel wagon structures: design, sizing and aplications. Retrieved from: Metalica. Retrieved: October 28, 2018.
