Pilatus Aircraft is one of the leading companies in the production of single-engine turboprop aeroplanes, and is the only Swiss company to develop, build and sell aeroplanes and training systems around the world. With the construction of the new final assembly hall, the production bottleneck in the main factory in Stans has been eliminated.
The client's requirements were clearly defined. He wanted an optimum building not only in economical terms but also with regard to all ecological aspects. Even the coloured exterior, for example, is not just any kind of paint. The environment-friendly paint is from the north of Finland and is a mixture of earth colours and fish-based paste,
with absolutely no poisonous ingredients.
On an area of 72 by 122 metres, the building, which resembles an aircraft wing, accommodates approximately 1,400 square metres of office space and the Visitor Centre, in addition to the 7,300-square-metre final assembly hall.
Digital building model
With regard to planning, the "timber builders" can also definitely be compared with high-tech companies such as the aeroplane manufacturer Pilatus, probably even surpassing them in terms of the number of individual timber components. For the complete structure, a digital building model was created as the basis for the entire construction planning. Here, approximately 33,000 timber components, 4,000 steel components and over 60,000 screws and dowels were electronically processed. The spatial structure of the load-bearing system was created by the design engineer using the CAD program Cadwork. It served the architects and all specialist designers as the basis for their detailed plans.
The timber construction firms were able to include the data directly in their CAD systems and transfer it to the CNC/CAM- controlled production and joinery machines. The result is impressive, the complete assembly of the main load-bearing system was completed within just a few weeks with very high fit accuracy of the components.
The supporting structure
The main features of the load-bearing system of the hall are the arched beams with a span of around 61 metres. The exterior shape of the hall is designed to resemble an aircraft wing. An arched roof over the assembly hall seals the building to the top.
The primary supporting structure in the form of framework consists of an arched upper boom, 36 x 120 cm, and a horizontal beam tie as a steel profile HE-B 260 or HE-B 300 in the bracing fields. The V-shaped framework bars, which are connected as tension or compression bars, connect the upper and lower booms and guarantee global buckling stability.
The beams are supported on the south side on well-formed wooden socketed stanchions inclined to the outside and, on the north side, on reinforced concrete fixed supports. In the area of the gable walls, the span of the formwork is reduced to the width of the entrance. The remaining section of the upper boom lies directly on the gable wall posts. Most of the supporting structure consists of glued laminated timber (spruce) of strength classes GL24 and GL28. Glue laminated timber of strength class GL36 was only used for individual, highly stressed elements.
The secondary supporting structure of the hall, which forms the actual roof level, is elevated on stilts above the upper booms in accordance with the cross-sectional profile.
Glued laminated ribs with approximate spacing of 35 cm in conjunction with the upper planking form the upper roof closure. These elements are prefabricated as in the workshop and installed as single-field elements. The outside walls also consist of wooden board elements, which were fastened on the outside to the primary supporting structure. They consist of wooden ribs with 200-mm rock wool insulation. On the hall side, they are planked by a 19-mm structural board and on the outside by 15-mm medium-density fibreboard. The façade made of sheet metal and a horizontal segmented frameworks were installed on them.
The horizontal stiffening of the hall is achieved by means of so-called K-frameworks. It initially transfers the horizontal forces from wind, excursion and earthquakes from the roof level into the arch level below this. The arch level, in turn, is stiffened by means of K-bracing, which conducts the forces on the north side into the fixed reinforced concrete supports and, on the south side, directly via the outside wall to the foundation. The lower booms are also stiffened by compression bars and horizontal bracing. This prevents buckling of the beam tie caused by wind suction stress. Transverse to the hall longitudinal axis, stiffening is by means of reinforced concrete supports and bracing in the gable axes.
The offices and the Visitor Centre on the north side have a skeleton structure. Wooden supports conduct the vertical loads from the roof to the foundation and prefabricated wall elements form the outer shell and guarantee the necessary rigidity.
The ceilings above the second and third floor are made of box-girder elements. The upper and lower planking is formed by three-layer boards glued onto ribs. These elements, also designed as single-field carriers, have spans of up to eight metres. The second and third floors, designed as an interposed supporting structure, form the Visitor Centre. It is 32 metres long and projects 7.5 metres beyond the north façade.
Frameworks with diagonal ties and a 32-meter span transfers the loads from the façade, ceilings and roof to the two gable walls. The real supporting structure is integrated in these walls and they transfer the loads via bracing to the foundation.
Assembly
The framework carriers were assembled from the hall floor. The individual trusses were preassembled in an assembly bed on the ground and placed in their final positions using two truck-mounted cranes. The trusses beside the bracing fields including the bracing were raised from the assembly bed and assembled in units of 8 by 63 metres using a total of four truck-mounted cranes.
Assembly of the roof and wall elements of the assembly hall, as well as of the office building with Visitor Centre, was carried out in parallel. Above all during assembly, the advantages of the integrated planning in the form of a digital building model again became apparent.
Although three timber construction companies were involved in the parallel premanufacture of the components, including the larger units, all the components were subsequently joined with the greatest fit accuracy on the construction site without a problem. All thanks to high-tech timber construction, which by no means needs to hide behind the competing materials of steel and reinforced concrete.
Timber construction is long-lasting
The planned duration of use of 50 years in accordance with SIA 260 will easily be achieved thanks to the careful design of the supporting structure. In addition, it will be ensured by regular monitoring and periodic maintenance measures. Pilatus Aircraft will thus be able to take off in the truest sense of the word with this impressive timber construction project. For this prime example of timber construction engineering demonstrates that the innovative power of today's modern timber construction companies is undiminished.
Pilatus Aircraft Ltd. - on the ascent for 60 years
Outstanding training aircraft from Pilatus Flugzeugwerke AG have been in use for the training of air force pilots for 60 years. For the development of the latest model, the PD-21, Pilatus invested 200 million Swiss Francs and now has a top product in this sector.
Pilatus has achieved exceptional success with its business travel aircraft, of which it has sold 750 since its market introduction in 1994. Planning at Pilatus is similarly ambitious. Annual growth of approximately 30% is targeted. In 2010 the turnover should reach a billion.
Project data for Pilatus assembly hall
Investment volume 28 million CHF
Capacity 120,000 m³
Floor area 12,050 m²
Year of construction 2007 to 2008
Construction time 13 months
