Covering a usable area of some 21,600 sqm and set hard against the railway tracks, Plot A plays a key role in the development of Lucerne’s Rösslimatt district. The 180m-long steel-and-concrete skeleton structure to which it is now home both responds to the requirements of its intended use as a university of applied sciences and provides flexibility. The reduced basement level provides plant and storage space, while the ground floor houses a refectory, an auditorium and the foyer complete with imposing staircase. Teaching and office space, the library and various meeting areas are located on the upper floors. Alongside lecture rooms, the fifth floor also boasts a cafeteria with a generous terrace overlooking the railway tracks.

The building’s location and its associated challenges called for meticulous planning of the load-bearing structure. Poor soil quality, for example, required the construction of over 600 piles to ensure the safe transfer of building loads. Similarly, its position immediately adjacent to the railway tracks imposed particular construction requirements in terms of vibration and noise protection. Meanwhile, the skeleton construction method and use of prefabricated ribbed slabs, columns and balcony slabs allowed a high degree of industrial prefabrication, which in turn made for a quick and extremely economical construction process.

The floors above the ground and fifth stories are in-situ cast flat slabs. Those over floors 1 to 4 were designed as 73cm pre-tensioned ribbed slabs in the edge zones and in-situ cast flat slabs in the central zone, the two joined together by pouring an additional 14cm concrete layer over the entire surface. The ribbed slabs are supported at the column axes on the beams that run the entire length of the building. The high rigidity values obtained by using ribbed slabs deliver lower vertical and thus foundation loads, improved vibration and earthquake behavior and increased resource efficiency, the latter further augmented by the use of recycled concrete for the joining layer. The floors above the ground and top stories are 44cm or 32cm flat slabs to allow for greater flexibility in terms of building plant and systems. The intermediate slabs are constructed using displacement elements (Cobiax system). The concrete saving achieved thanks to the void formers results in lower dead loads, which once again offer both superior vibration behavior in case of earthquake and greater resource efficiency.

The internal and external columns, ribbed slabs and wrap-around architraves and balconies were all designed as prefabricated elements. The interior facade columns are arranged in a 6m longitudinal grid, a multiple of the basic 1.5m grid that runs through the entire building and out to the external balcony supports. The central circulation cores brace the building against horizontal wind and seismic loads. The basement level features a watertight yellow tanking barrier. Foundation loads are transferred to the ground via in-situ cast concrete displacement piles.

Building so close to the railway tracks presented some specific challenges, particularly in relation to the potential for vibrations. Based on the findings of the vibration report and further investigations, the slabs were designed with a natural frequency of approx. 13.5 Hz to avoid resonance effects, with the slab over the fifth floor having a natural frequency of 10 Hz. The construction heights of the slabs and load-bearing elements were specified to achieve the required level of dynamic rigidity.

The Rösslimatt redevelopment scheme has enhanced access to Lucerne railway station via the Frohburgsteg footbridge (Plot H). A new 5m-wide stairway resting on five intermediate truss-like supports runs parallel to the footbridge. The individual vertical steel members splay outwards in a V-shape as they rise to create a series of five fan-shaped supports. The foundations are set on micro-piles driven into the unstable subsoil to take the vertical and horizontal loads. The steel-and-timber structure sets new standards in the way it links the new development to the existing Bahnhofplatz, while the upgraded footbridge provides a visual connection with the look and feel of the new building. The lightweight frame of the staircase and the ‘flying’ roof combine to make a fitting gateway to Rösslimatt.