'Bridge buildings' across the highway
The Grotiusplaats plan area lies between Central Station and the Beatrixkwartier in The Hague. Since the construction of highway Utrechtse Baan the area has been severely segmented, and it needed to be reunited into a spatial and functional entity. On the initiative of the chief government architect, a team of architects was brought together under the leadership of Joan Busquets. The architectural studio ZJA were commissioned to design two office buildings above the Utrechtse Baan.
The Grotius plaza is surrounded by offices, shops and dwellings. The sunken Utrechtse Baan motorway cuts straight through the square. ZJA was commissioned to design two office buildings above the Utrechtse Baan. The two 'bridge buildings', parallel with each other, span the Utrechtse Baan and form a forceful demarcation on each side of the central square. Like stitches in a wound, the buildings connect the north and south sides of the square. These buildings are conceived as gateways, both at street level and driving on the Utrechtse Baan. The office blocks are raised two storeys above the level of the square in order to create as much openness as possible. A glass entrance and a transparent shop space are all that stand beneath. In order to establish a connection with the ‘canopy plan’ of the urban design, the the first office storey above the glass substructure is set back from the facade. This floor is suspended by tie rods attached to the floors above.
The bridge building on the west side has five storeys of office space, while the building on the east side is the same height but has a number of extra storeys in a tower-like structure. Access to the building on the west side is situated in two cores on opposite sides of the Utrechtse Baan at street level. These cores also provide structural stability. The building on the east side has three entrances at ground level.
A load-bearing structure of steel lattice trusses makes the big span across the Utrechtse Baan and is left visible, defining the look of both buildings. Structural, concrete facade elements are affixed to the steel lattice trusses. The enclosure of the facades is different on each side of the two buildings. The elevations overlooking the square have a glass curtain wall, while the exterior elevations are stone-like, just like the urban elevation of which the buildings are a continuation.
The designers had to demonstrate that the building’s fire safety would satisfy regulations without the need for additional fire-resistant cladding (in order to get permission to leave the steel load-bearing structure bare). Research demonstrated that the considerable mass of steel and the relatively large surface area of the elements used would ensure rapid diffusion of the heat. If the structure were to heat up in the case of fire, the steel directly releases the heat into the atmosphere. It required no more than a slight increase in the size of the elements to guarantee the building’s fire safety.