On the premises at Sloepenstraat in Ostend, the SNCB built a new traction workshop with two parallel train tracks for the repairs of train carriages and locomotives. Establis did the implementation study for contractor Franki Construct (Willemen Groep). The project was not only fairly unusual because of its size and the large loads that train carriages entail. A lot of detailing also had to be designed to make implementation possible.

The new building includes the 200-metre-long and 16-metre-wide hall with the train tracks on one side, and the adjoining offices and social areas on two floors on the other. The office part is made of hollow concrete blocks and floor slabs that bear from the outer façade to the hall façade.

‘Artistic’ foundation slab

The workshop itself has full-length train tracks laid on raised columns, making it easier to see and work under the train. Part of the work involves replacing and touching up train wheels (2 tonnes per wheel!), and this every time after 200,000 kilometres. The (bottom of the) foundation slab is nothing like the ordinary flat slab normally found in industrial buildings. The railcars create enormous downward forces, as do the mobile jacks that push the trains upwards. Several drip pits - for oil, and other substances - are embedded in the floor, and a pipe duct / technical basement runs the entire length of the building between the two train tracks. Because of all these elements, the underside of the foundation slab can be described as ‘artistic’ in shape, to say the least. This obviously required a lot of engineering and calculation work. On top of that, we also had to take into account underground conduits, which were at risk of conflicting with the outlined reinforcement. Because of the length of the building, an expansion joint was placed between each 45-metre long section. Due to the complexity of the foundation slab, this required additional detailing.

The poor subsoil meant that the entire building had to be founded on piles. Additional challenge was the presence of 2 large old vaults or foundations in the subsoil - their former function was unknown - which were built too robustly to be removed. The positioning of the foundation piles and calculation of the spans thus required a lot of adjustments. Interestingly, the pipe duct was not placed on piles, but was suspended from the floor slab.

Columns and trussed roof

The superstructure of the workshop is made of steel columns encased at the base. The roof contains a truss structure. Because both ends of the building can open to allow a train to pass through, we had to take into account the upward forces the roof may experience in the process due to the draught. Additional complexity with the roof trusses is that the building contains 2 rolling bridges that can move towards each other and transfer their loads to consoles on the columns. Below this, a 2nd console is provided on each column for a mobile work platform to inspect the top of the trains. When parts of the train set, the rolling bridges, a working platform and one or more mobile jack(s) come together in one location, locally very large loads can be generated on the floor and columns. This also had to be thoroughly studied and analysed.

The walls of the workshop are made of cellular concrete panels with corrugated steel cladding. On both long sides, just below the roof, there is a polycarbonate strip along almost the entire length, bringing daylight into the hall. One side also contains vertical glass strips, and there are skylights in the roof. To prevent all these openings from weakening the façades and the roof, we used additional steel structures.

Assembly crane

Our original task in this project was to study the structural integrity of the design in function of the implementation. However, from our experience in large and complex projects, we quickly saw in which areas additional engineering and calculating work was needed not only to achieve structural integrity but also to ensure efficient and correct implementation.

In addition, we also conducted the structural design for the outside, including a run-on slab for trucks to drive on and a track for a maintenance train. Because there was no room next to the construction site for the 80-tonne assembly crane for the steel structure (columns and roof of the workshop), we also made it possible for the crane to do the assembly work from the new floor slab inside the building itself.