Friesland Bank

Leeuwarden is the capital of one of the northern provinces of the Netherlands. Its townscape has an average height of 3 to 4 stories, with a business centre of 10 stories and an occasional solitary 100 m high office tower. On top of an existing building complex of the headquarters of the Friesland bank, consisting of three existing and one new office buildings built in different recent decades. a glazed dome has been built. It is covering an internal atrium and is clearly visibly in the skyline of Leeuwarden town. The dome is composed of a single-layered space frame in network geometry, fixed between three triangular space frame trusses.

The horizontal diameter of the dome is 28 meters. The main frames of the three trusses intersect in the top of the dome. From these three delta frames, the three space frame parts are suspended and stabilized. In vertical cross-section, the height of the spherical space frame structure is slightly over 14 meters. One of the three space frame parts is downward elongated (12 meters) as a suspended curtain. Furthermore, the lower side of this suspended façade structure supports the dead load and live load of the adjacent flat glazed roof, which is approximately 28 x 28m². This enabled the architect to realize an atrium without internal columns, which is clearly seen in photographs taken from the ground floor looking upward.

This additional dead load from the flat glass roof, not the wind, proved the governing load combination, in spite of the 26 meters height of the dome. The delta trusses are necessary, as the existing buildings could not support the dome structure. Thus, this jacket skeleton stands with 20 meters high concrete legs on the foundation. All three legs are stabilized side-wards at the bottom of the dome by the adjacent buildings. Triangulated delta frames of welded tubular construction are positioned on top of the prefabricated concrete legs. All are connected together to the summit. The single-layered space frame is connected to the central lines of the delta trusses, so that these seem to form a unity with the space frame. In fact, the dome is suspended between the trusses.

The building complex realized in the centre of Leeuwarden dominates the sky like St. Peter’s in Rome, Italy and the dome of the Reichstag in Berlin, Germany, freely towering above the silhouette of the city.