185 Introduction At the moment, the communal services are scattered on different locations around the coastal town of Koksijde. The town of Koksijde organized a competition, to build a new town hall in the centre. Storme-Van Ranst made the design and the engineering studies of this project were entrusted to VK Engineering. General description The building consists of 2 office wings, with an atrium in between of 25 by 25 metres, with a clear height of 20 metres. The office wings count 4 floors above ground level, which contains landscape offices. Slender steel constructions and the glazed atrium symbolize the transparency the town council wants to emanate. The building can be accessed by a footbridge on the ground level, and also has an entrance at the lowered square in front of the building. This lowered square can be accessed through huge steps, which can also be used as sitting benches during events. In this atrium stands the central council chamber shaped like an elliptic structure, “floating” above the ground. Technical data Client: Town of Koksijde Architecture: Storme-Van Ranst Start date of works: April 2004 End date of works: December 2006 Glass façade atrium: 30 x 22 m (width - height) Measurements atrium: 25 x 25 x 20 m (width - length - height) Height columns: 6 m Diameter columns: 711 mm Thickness columns: 25 mm Measurements elliptic volume: 14,5 x 19,5 x 11,5 m (width - length - height) Importance, approach and result Office wings The entire building stands on a steel foundation, shaped like a floor plate. The office wings are constructed with columns and beams, that carry the on-site cast monolith floors. The flat plate floors guarantee a maximum of flexibility in arranging the office space. The ceiling plate stays visible and is used as a massive element in the night cooling process. Atrium The atrium is formed by the sidewalls of the office wings and by two impressive glazed curtain walls, supplying extra transparency. In order to neutralize gusts of wind, horizontal trusses on each level support the glazed surfaces. The roof of the atrium is shed-shaped, with slanting sandwich boards and vertical glazing, in order to allow a levelled entrance of the northern daylight. Central council room The elliptic volume stands on 4 metal supporting columns, all slanting, and 6 meters high. All building services of the council room are housed within these columns. One ‘leg’ contains electricity and cables for data, another the plumbing. The other columns function as the supply and drainage of air of the HVAC-installations. The council room is accessible through footbridges, connecting to the main footbridge that connects the two office wings. The elliptic structure contains 3 levels. • A technical room, transformable into an informal meeting room. • The council room • A public area The volume is constructed from 12 vertical elliptic trusses, consisting of round steel pipes. Horizontally, connecting rings were inserted, also consisting of round steel pipes. Inside the elliptic structure, 2 horizontal platforms form a pulling construction, preventing the trusses from opening up. The platform on the public level is hanging from the vertical trusses, in order to avoid disturbing supporting columns in the underlying council room. The transit of the building services could not be interrupted at platform-height. The platforms were fixed with welding and bolts on massive transverse plates, with openings roasted in. The steel structure is filled in with laminated elements, made specifically to fit. On top of this framework, a wooden boarding is attached, serving itself as rest for an aluminium coating. The inside of the volume is finished with insulation and a gyproc-coating. The entire construction has a fire resistance of one hour, by means of fire-resisting paint that was applied after assembly. SCIA software VK Engineering created a 3D-drawing model of the entire construction that served as a working base for the architect and a starting point for all further execution drawings. The entire construction was modelled in 3D-software, keeping all necessary degrees of freedom in mind. After calculating the structure, the most important distortion appeared to occur in a horizontal rotation, resulting from the slanting position of the supporting columns. This distortion was important for the locating of the main footbridge with the connecting footbridges that access the elliptic volume. City Hall Koksijde
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