CONSTRUCTION OF A NEW PRODUCTION HALL FOR VOLKSWAGEN AG BRATISLAVA WITH PRE-FAB PARTS

In addition to the usual permanent forces (dead load, design load) and variable loads (snow, wind, earthquakes), the client has specified further technological  loads, which have proven to be quite relevant for structural design according to the STN EN. For the levels 4.50 m / 5.40 m, characteristic roof load capacities of 7.5 kN/m², 20.0 kN/m² and up to 22.0 kN/m² were prescribed. For the remaining levels +9.00 m and +13.00 m / +14.00 m they were 7.5 kN/m² and 10.0 kN/m². The variable roof loads were 1.5 kN/m².

The characteristic point loads on the floors achieved values of up to 407.0 kN, but were around 100.0 kN to 200.0 kN on average. The suspended loads on the 12 m long trusses were between 76.0 kN and 87.0 kN. it was not possible to find a structurally viable and at the same time economical solution for the 24 m long prestressed binder with limited overall height. For these reasons, further project alterations for structural optimization were required. A further hurdle was the given temperature difference between inside and out of around ±30.0 K. The environmental conditions of the exposure classes XC1 and XC2 as well as fire protection requirements R60 had no influence, however, in the static design of the structure.

 The engineers of the DeBondt office started in December 2009 with the execution planning and the associated re-engineering of the entire structure. This planning work thus ran parallel to the already started construction and extended from January 2010 to the acceptance in June 2010. The planners who had designed the original skeleton construction in in-situ concrete were also commissioned by the client with the test statics, although these are not according to Slovak standards mandatory mandatory. The foundation works as well as the foundation foundations on large piles and the base plate of the level ± 0.00 m were done by another supplier of the general contractor.

The basic dimensions of the object and its division into three sections as per the original plans were maintained. The originally planned steel structure for the roof was replaced in the reworked planning with pre-stressed and pre-cast concrete. The floor slabs were designed as a combination of in-situ concrete and filigree slabs stored on a grate made of precast beams.

The main vertical load-bearing sections are precast columns with a total height of 24.0 m and a rectangular cross section of 1000/800 mm and 800/800 mm respectively. The supports are clamped in in-situ concrete quiver. An exception is the connection axis to the existing hall 2. Here, the columns are borne on a coupling anchor of type PFEIFER PSF 30.

The biggest challenge of the project was the statics calculation and economic assessment of the supports, as the only present elevator shaft (6 m x 4 m) is not suitable as a stiffening core. The supports must thus ensure a horizontal stability of the structure. Thus, on every floor level, a continuous pre-cast beam with a rectangular or reverse L-cross section was implemented as a comprehensive bracing measure. The optimum static solution was found using the program BEST by RIB. The engineers determined this using the second order analysis taking into account the necessary imperfections and the effective stiffnesses of a variably reinforced cross-section with potential crack formation on the side under tension. In this way, they were able to achieve economic dimensioning while ensuring the adequate buckling safety of all columns.

The engineers were able to demonstrate support loads from the perimeter assembly, from ceiling beams and trusses with the RIB RTool software. The result was short consoles using elastomer supports and high-strength in-situ concrete mortars. 

 The structure of the corrugated roof is a system of pre-stressed and pre-cast trusses with a length of 24.0 m and a height of 1.4 m and 1.5 m, supplemented by reinforced concrete trusses with a length of 12.0 m and height of 1.2 m and 1.05 m, as well as 12.0 m long purlins with a wedge-shaped, 650 mm and 700 mm high cross-section. Figures 5 and 6 illustrate  the arrangement of the corresponding roof components.

The pre-stressed, 24.0 meter long pre-cast trusses were found to be the most efficient solution for the given height restriction and the fire protection requirements. The complex statics design of the pre-cast trusses, incl. influences such as transport systems, technical recesses in the transverse direction and non-linear tilt protection, was carried out with the software RIB RTfermo.

The load-bearing structure of the interior floors in the technical area was formed of a girder grid of 1,500 mm high main beams (12.0 m x 12.0 m) and notched, 950 mm high joists and rib beams of 3 m each. The actual roof was a composite structure of 60 mm thick pre-cast panels and 140 mm in-situ concrete. The concreting was carried out in large sections, where the largest single operation was 36.0 m x 36.0 m. Here, the process was carried out in such a way that, along the bearings of the rib beams against the joists, a 1 m wide expansion joint was left, creating two construction joints. Here, the upper reinforcements were laid in such a way that they were not loaded at the same time from both sections. Finally, the strips left out were filled.

During the entire construction process, precise execution of connections and details was required. Important here were, for example, the formation and compound effect of the stiffening  beams. These, together with the ceiling plates, function as a continuous beam. Through static calculation and dimensioning  of the main beams and joists in the program RTbalken by RIB, the engineers were able to keep to the tightly limited deflections required by the installed technology. In the same way, with the stiffening  beams, they took account of the torsional loads occurring there in measuring the system.

THE PRE-FABRICATED PARTS ARE MADE OF THE FOLLOWING MATERIALS: