What are Posi-Strut beams, how are they made, what advantages and usages do they have in the building sector?
What is a Posi beam?
Posi-Strut or Posi-Joist beams are a typical product of MiTek Industries and they consist of combining 2 wooden elements (the top flange and the lower flange), through the metallic types of Posi-Strut Beams. Depending on usage and on the structural analysis, there can be various types of beams, with heights varying from 202 to 421 mm and widths from 72 to 150 mm latticework, into one compact, sturdy and rigid element that presents numerous advantages which we will discuss further in this article. Other products that can be manufactured through MiTek technology are wooden trusses for roofs and attics or buildings with wide openings.
Tipuri de grinzi Posi-Strut
În funcție de aplicații și calculul structural, rezultă mai multe tipuri de grinzi, cu înălțimea cuprinsă între 202-421mm și lățimea tălpii cuprinsă între 72-150mm.
As with any wooden structure, it is highly important that the wood which is being used in the production of beams is top-quality wood with a strength class of C24 and maximum humidity of 18%. The metallic lattice works are part of the ”MiTek connectors' category and they are made from galvanized sheet-iron of 1mm, according to EN10143:2006 and EN 10346:2009.
The Posi beams’ manufacturing process needs a special hydraulic press with which the multi-pin end pieces of metallic latticework are secured in the wooden elements according to the manufacturer’s specifications. We manufacture them with a 30 tonnes force. The affixation of metallic connectors through thrusting is forbidden.
Apart from floors, Posi beams can have multiple uses in construction work. They can be used as soldiers in a timber frame structure ( in the formation of prefabricated walls) or truss frames for timber support and attics ( they are also known as Posi-Rafters). When combined with attic trusses, it results in a prefabricated robust element which is known as Posi-Attic.
The advantages of the Posi-Strut beams
The prefabrication technology offers multiple advantages from the angle of wood structures quality, the fast production time, and optimizing wood consumption. In terms of Posi beams, we specify the following advantages:
1. The low wood consumption compared to traditional beams: the metallic lattice practically replaces the center of the beam, therefore reducing wood consumption by over 50%. Consequently, the weight of the floor is reduced by 30% compared to the one made from balk or lamellar wood and by doing so the assembling can be done by precast elements.
2. Wide opening without protective casing: a beam can reach up to 9m aperture, depending on the beam’s height and the structural analysis. Moreover, beams can be manufactured with adjustable ends for possible beam interlockings in case a building is refurbished and the floor is replaced.
3. Enhanced solidity and minimal vibrations in the floor: the metallic latticework successfully absorbs the charging and the vibrations created by occupants. Furthermore, bracings between beams deliver more efficiently the loadings allowing an easier transfer of the single forces, without raising the beam’s height.
4. Floor equipment: the metallic latticework allows the protraction of equipment such as ventilation ductworks, wirings, and sewage pipes, without other ports and perforations. The headroom between beams’ soles vary between 108 and 327mm and it suffices for any type of ventilation ductwork. As far as the nZEB (nearly Zero Energy Building) standard, the heat recovery ventilation unit plays a very important role in the economy of an effective and healthy house. We have written more on nZEB in this article.
5. Reduced thermal bridges: if the beams are used in the production of timber-frame walls, floors over groundwork, roof timbers, or platforms, then they are part of the building thermal envelope. Therefore, if we use prompt insulation (cellulose, straw, wood fiber flocks), it evenly fills all the gaps between the latticework of the beams, therefore the thermal bridge is reduced substantially. We have extensively discussed thermal bridges and the principles of the passive house in this article.
6. Optimized production: beamline production efficiency can reach 200ml/hour depending on the type of press used. The length of the beam is boundless because the wooden soles can be extended with MiTek connectors and thus we are no longer conditioned by the standard length of the timber. This way wood loss from cutting is also diminished.
Conclusions
The Posi-Strut or Posi-Joist beams represent an advanced option of the traditional wooden latticework beams and they offer undeniable advantages, both optimizing wood consumption, and mechanical properties and the ease of putting them into practice. Moreover, they are highly versatile and they are not only suitable in wooden construction works, but also in brickwork when they successfully substitute the concrete slab. No doubt that there are many more things to be discussed about Posi usages, therefore do not hesitate to contact us for questions or technical details.