The Provinciehuis in Antwerp, designed by Xaveer De Geyter Architects, is a photogenic and impressive building. The engineers of the German firm Bollinger+Grohmann devised an intelligent structure that keeps the tower standing.
In 1960 Ada Louise Huxtable defined the successful balance between construction and architecture: ‘The fusion of structural function and abstract form creates a kind of building that is so fundamentally right that most other architecture seems superficial beside it.’ Buildings must show that they have come out on top in the battle with gravity, without being too triumphant or heavy-handed about it, but without pretending that it’s nothing special either.
If there is one recent building in Belgium that has taken this struggle to heart, it is the Provinciehuis in Antwerp, designed by Xaveer De Geyter Architects, with Bollinger+Grohmann as structural engineers. The Provinciehuis is often described as an object or as a spectacular icon. In an interview with Sarah Whiting in a recent issue of El Croquis devoted to the work of XDGA, De Geyter talked about ‘a deformed volume that makes it an iconic object’. What is special about the Provinciehuis is that the building is an integral structure, like a coherent collection of elements. What makes the project singular is the way in which the form becomes possible thanks to the construction.
The upper eight floors of the volume of the Provinciehuis swing away to the south, taking the north-west corner as their axis of rotation. Each floor thus turns a little more backwards. Making this turn possible was the biggest challenge for the engineers, with the additional difficulty of the entrance hall on the ground floor, perpendicular to the main building, which spans the hall at the bottom like a bridge, creating a public terrace in the process.
Paradoxically, the Provinciehuis is supported by the element that embodies the ‘twist’ of the building par excellence: the façade, composed of triangular window and wall elements made of reinforced white exposed concrete. The main challenge for the structural design was reinforcing the tower, taking into account both the unusual alignment due to the twist and the wind loads. The load-bearing but perforated façade also makes it possible to omit columns on the floors, resulting in spans of 19 to 25 metres. Yet other elements also form part of the structure. Two circulation cores in black exposed concrete help to ensure the rigidity of the building, and the floor slabs also play an important role in transferring the vertical loads. On the fourth and fifth floors, three steel trusses span the lower part of the building: the outer trusses are embedded in the concrete and function partly as a composite structure, but like the wall they also have to be spatially curved, and yet never exceed the thickness of that wall.
The story of the structure of the Provinciehuis has many more exciting episodes, such as the parametric geometry studies, the weaving patterns of the reinforcement steel, or the combination of pile and slab foundations. Many of these episodes are the result of a kind of functional and rational formalism, prompted by the realization that some public buildings should stand out, perhaps even more so in the twenty-first century than before.
