197 Introduction The various judicial services of Antwerp urgently needed new law courts, as they were suffering from an acute lack of space and being scattered all over the city. At the request of VK, Richard Rogers and Arup signed up for the public competition for new law courts on the Bolivar place, organized by the Buildings Agency. The project of the temporary association RRP - VK - Arup is a gateway for Antwerp, entering or leaving the city from the south. It stands on a prominent place, at the end of the “leien” (main streets of Antwerp), on a location where Antwerp always has had a focal point, that is ‘The Spanish Citadel (from 1571 until 1894) and the South Station (“the cathedral of the South”) until 1966. Furthermore, the law courts project was seen as part of a revitalization process of the south of Antwerp. Description The new law courts are designed as an open house. Large glass surfaces connect the judicial services with the citizens of Antwerp and offer marvellous sights on the city. This not only enhances the transparency, literally and figuratively, but it also insures a good system of finding one’s way. Sustainability was another key word. The Buildings Agency stipulated that they wanted a building that didn’t need mechanical cooling in the offices. As such, the law courts make an architectural as well as an environmental statement The construction counts 6 office wings, placed around a central public space, the ‘Salle des Pas Perdus’ (Hall of Lost Paces). From the Bolivar place, a monumental staircase mounts up to this imposing but light reception space, which acts as an extension of the public square. From the hall, 6 office wings stretch out (3 on the left and 3 on the right hand side) and are connected on the 2nd floor through walking galleries. The more public functions are situated directly near the hall; the parts that are more inaccessible for the public are situated further down the wings. In between the office wings, inner yards were laid out, offering a green sight for the office workers and cooling down the warm air that flows between the office wings. With 1 level underground (cells and parking) and 5 levels above ground, the building measures not higher than 15,75 metres. The complex circulation-system of law courts, in order to protect privacy and for security reasons, demands that private and public circulation are clearly separated. Therefore, the project team decided to put the actual courts (26 smaller courts and 6 larger courts) on top of the building, above the offices of judges, administration, … In this configuration, the courts almost float above the building and are crowned with striking cone-shaped roofs. The roofs on the large courts peak at 41 metres above ground. Technical data Public tender organization: Buildings Agency End user: Federal government service of Justice Architecture: Richard Rogers Partnership - VK STUDIO - Arup Duration of the works: April 2001 to October 2005 Surface terrain: 3,7 ha Gross surface: 78.000 m² Facade height: 18 metres Facade width front: 300 metres Facade width back: 240 metres Roofs on courts Start placement roofs: July 2003 End placement roofs: mid 2004 Height large roof: 25 metres (41 metres above ground) Height small roof: 7 metres (18 metres above ground) Weight large roof 24 tons Weight small roof: 18 tons Gauge inox coating: 0,4 mm Surface inox coating: 16.000 m² Roof structure public hall Start placement steel structure: March 2004 End placement steel structure: June 2004 Measurements: 60 metres x 70 metres Weight steel construction: 240 tons Painted surface steel structure: 2.400 m² Importance, approach and results Roofs of the law courts The pointed roofs are without a doubt the most striking characteristic of the law courts. The applied structural concept, material and construction method resulted from a thorough analysis, considering all pros and cons of the various options. Through wind tunnel tests, the most unfavourable wind charges were determined and wind disturbance on the surroundings analysed. The results of the tests, combined with other forces (influenced by temperature, snow and finishing materials), gave the necessary data to be able to calculate all structures three-dimensionally. Also, the calculated distortions of the structures had to be checked with the compliance of the finishing materials. At the end, the project team opted for a hyperbolic paraboloid or hyparscale. This figure has a great advantage: it can be constructed from linear elements, allowing for a simple method of covering and coating it. One roof is composed from 4 connected quadrants (2 high and 2 low quadrants), each a hyparscale in a square base. The linear elements, as a filling-in of the quadrants, are executed in a “woven” wood-structure, using planks screwed on top of one another and fixing them on a centring. This allows for the coating to follow the curved form perfectly. The wood-structure is left visible on the inside, for the public to view the forces within the structure. During the conception phase, all possible finishing materials were considered. The hyperbolic paraboloid form of the roofs, specific connecting details, maintenance demands and sustainability and the transition from horizontal to slanting planes decided in favour of inox. Folded stainless strip steel was welded together by means of a continuous weld. The quadrant-construction-method made it possible for the roofs to be constructed completely off-site. After their transport on the river Scheldt, the segments were connected and mounted in a minimum of time and without scaffolds. The pointed roofs act as membranes, all charges are transferred to the underlying structures through normal forces. Roof of the central public hall The roof is a complex spatial structure, composed of triangle sections. Several junctions and points of support, situated at several levels in the space, hold the entire roof together. Eight of these points of support are spatially fixed: they are situated at the ground level of the central hall, in between the office wings. Six other junctions are situated at the concrete platforms of the large courts and are floating. This means the roof structure can’t be used to transfer the gravitational forces of the six high pointed roofs of the large courts. The roof structure is a grid of linear and spatial metal bars, connected through hinging joints. The pressure of the roof is resting on the top girders, which are connected with vertical rod resistors to subtending cables and bars. Horizontally, the roof offers support for the façade at the front and the back, but vertically the roof is completely unattached. In other words, the roof rests only on the 14 points of support mentioned above, not on the facades. Footbridges without intermediate support and as wide as the central hall hang underneath the roof construction. They connect the office wings on both sides of the hall. As well as the charges of its own weight, the roof is covered with doubled-glazed frames and sandwich boards. The glazing is doubly isolated, in order to prevent condensation. The most important external charges are snow and wind. In order to withstand these influences, wind tunnel tests were applied. A CFD simulation tested the roof structure in case of fire. The results showed that the temperature of the steel construction would not rise above 140°C in case of a standard fire, making it unnecessary to provide the structure with a fire resisting paint. Roofs Courthouse Antwerp
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