On the 9th of February 2015 the ‘Dutch Construction Awards 2015 have been distributed. The cablenet facades of the Market Hall – realized by Octatube – were awarded in the category for building materials and systems.
The Market Hall has been designed by Winy Maas of MVRDV and the structural design was drawn by Maurice Hermens of RoyalHaskoningDHV. On behalf of the main contractor JP van Eesteren and based on its expertise in light weight structures, Octatube has taken full responsibility over the engineering, production and installation of the cable facades.
The two cablenet facades are 34 meters in height and 42 meters wide. The cables have been pre-stressed in between the concrete arch and the foundation of the building, closing the building at both sides. The galvanized steel cables have a diameter of 31 millimeters and are fixed in heavy steel boxes, embedded in the concrete structure. The 22 horizontal and 26 vertical cables are the only structure of the façade and the cables divide the glass surface in a grid of 1.5 by 1.5 meters.
By means of a hydraulic tension bridge the cables have been pre-stressed step by step with a maximum applied pretension of 300 kilonewtons per cable. During this operation the cables have been stretched around 150 millimeters each. The cables have a surplus capacity of 50 kilonewtons to absorb the impact of creep in the concrete over the first couple of years.
The maximal theoretical wind load can cause the façades to deform 700 millimeters inwards and outwards. Although this is one of the characteristics of cable facades, an amplitude in the middle of the glass surface of 1400 millimeters is considerable. Under such deformations the glass panels are protected against too much torsion by special rubber profiling at the corner fixation of each laminated heat-strengthened glass panel. Also the silicon joints in between the glass panels contribute to the flexibility of the façade. However, in the corners of the façade the glass panels are fixed on 2 sides. Here only one corner of the glass panel can move, causing substantial torsion of the glass surface. Octatube has dealt with this by employing its more than 10 years of experience in cold bending and twisting of glass. The regularities and the ‘do’s and don’ts’ were well-known. Also the solution at the revolving doors has been engineered and built to incorporate deformations in the glass surface. The steel portals of the revolving doors are fixed to the cable structure with a hinged connection at the ground floor level, causing them to ‘sway’ with the façade during heavy storms. Since its creation in 1983, Octatube has ventured in the niche of structural design of facades and roof lights: tensile structures, spaceframes, glass structures, cardboard structures and composite structures with glass-fiber reinforced plastic. Incremental innovation (on modest scale, with small steps ahead) has been the guiding principle in the past 30 years and the pursuit of innovation remains Octatube’s trademark. Sometimes innovation was even radical, such as with the GRP shell roofs for the Rabin Center in Tel Aviv or with the cardboard dome in IJburg. For a medium-sized enterprise like Octatube with 85 employees, small steps are the best way forward to point the construction sector in the direction of innovation.
Photo credits: Ossip van Duivenbode