Prestressing inside mould Aannemersbedrijf VOF Noord
Hendriks precon, for Aannemersbedrijf VOF Noord in Nieuwegein, designed and constructed a 37-m-long and 3.5-m-wide mould for prefab prestressed floor slabs. What is special about this is that the tensioning device is incorporated into the mould. This gave the builder production and scheduling flexibility without having to make expensive investments in the floor at the temporary location.
Aannemersbedrijf VOF Noord in Nieuwegein develops and builds prefab apartment buildings. The company is currently involved in the high-profile redevelopment of the Rijnhuizen district in Nieuwegein. VOF Noord is constructing residential buildings here, such as De Ontdekking [The Discovery], Terraza and Fulton Park. The production of the prestressed floor slabs is temporarily taking place on a still-to-be-developed piece of land in Nieuwegein. The plan is to move to another location, as soon as the residential construction permit has been issued. Directeur Ronald Berger of VOF Noord: ‘We started to produce the prestressed floor slabs ourselves, because our supplier’s delivery lead times were increasing and we had our deadlines to meet.’
Berger purchased hydraulic prestressing cylinders (from the company Goes Bouwtechniek in Heteren, the Netherlands). They approached Hendriks precon for the mould. While concrete is able to withstand compressive forces very well, it does not withstand tensile forces very well. Reinforcement using steel wire strands overcomes this weakness. These are placed inside the concrete under tension. Commercial director Jan van Alfen of Hendriks precon: ‘We installed a mechanical device inside the mould so that the initial tension is transferred to the edges. This is rather special. A frequently used alternative would be to install indenters in the production floor. But that requires expensive anchoring devices to be installed in the ground and due to the temporary nature of the current operating location, this was not a desirable option.” Hendriks has supplied many hundreds of metres of slab production lines. The moulds used for this purpose comply with the crucial requirement that the formwork’s floor must be 100% flat to produce high-quality walls or floors. The CUR 100 B2 flatness criteria is no problem for Hendriks precon.
Directeur Ronald Berger of Aannemersbedrijf VOF Noord is very satisfied with the solution provided by Hendriks precon. ‘We are now operating at approximately 80% capacity and producing the slabs ourselves helps us achieve the agreed-upon delivery times without any overruns. We still have many apartments in the pipeline for the coming years, so for the time being we can move forward.’ Over time, the moulds installed at the temporary location will move to the planned new VOF Noord location. Berger: ‘We are still looking for a suitable location.’ Van Alfen: ‘Once we have found our new site, the 37-m-long and 3.5-m-wide moulds will be moved there and once they have been installed, we will extend their length to 60 m at the permanent location.’