The use of BauBuche also requires the use of special screws and steel fasteners approved for BauBuche. The trusses of the production hall are therefore equipped with suitable fasteners produced by SWG Production themselves, especially ASSY® fully threaded screws – or more precisely the ETA (European Technical Assessment) of the Pollmeier BauBuche (ETA-14/0354) in combination with the ETA of the Würth ASSY® fully threaded screws (ETA-11/0190). Decisive for the safe use is the link of the two ETA’s, i.e. the reference that the respective ETA makes to the other. By coordinating these two products, the manufacturers give the user and structural engineer the certified assurance that they can use them together. ASSY® fully threaded screws, however, can also be used for softwood.
ASSY® are self-drilling screws made of specially hardened carbon steel or stainless steel with anti-friction coating and corrosion protection. The thread outside diameters available up to now are between 3 mm and 14 mm and the total length of the screws is between 13 mm and two meters. Due to the large dimensional variability, this screw type could be used for all truss girders, i. e. the main, secondary and stiffening trusses.
For the processing and assembly of hard wood components special material-specific tools are required, such as for pre-drilling and inserting the screws. ASSY® is a self-drilling screw that does not require any pre-drilling. Pre-drilling of BauBuche components is nevertheless advisable due to the high material density. Apart from the fact that the screw positions are already defined, which is particularly helpful for a large number of screws, as e. g. in the case of the nodal junctions of the production hall, since they do not first have to be marked out on the construction site. This saves time and staff and helps to avoid mistakes. Pre-drilling also enables the screws to be inserted into the components according to plan and to a precise fit, thus ensuring the necessary process reliability.
Due to the high material density of BauBuche, it is also important to ensure that shorter screws with larger diameters are used rather than long thin ones. And last but not least you need a high torque drill to insert the screws.
The structural designers of the in-house engineering office SWG Engineering have designed many nodal junctions as carpenter-based connections, but have adapted and optimized them accordingly with regard to the use of BauBuche. This was also due to the fact that the simple geometries of these proven wood joints bond well and the components can be joined without constraint – and at the same time with optimum power transmission in the nodes.