Over 2,700 custom engineered natural rubber bearings for a new correctional facility in The Netherlands.
The Zaanstad Project, commissioned in 2016, comprised the construction of a new correctional facility in the Netherlands holding up to 1,000 detainees across 600 cell blocks. The cell blocks were delivered to site as prefabricated units and were to be installed at a rate of 24 units per week, in line with a short construction schedule.
Farrat local partner Plaka Nederland, was approached to provide an effective resilient seating and acoustic isolation solution that could; support the load of the units using small elastomeric bearing pads (resulting in high contact pressures up to 10 MPa), provide long-term acoustic decoupling, and accommodate lateral displacement. The solution required a maximum thickness of 30 mm and limit the maximum deflection to 2 – 3 mm. Despite the deflection limitation, the isolators also had to facilitate airborne and impact sound insulation performance of 51 DnT,A and 59 dB LnT,A.
Having understood the parameters of the challenge, Plaka Nederland collaborated with Farrat to develop an isolation system that incorporated over 2,700 natural rubber bearings. Farrat’s Pad Performance Calculator was used to calculate the dimensions of the bearings, the natural frequency and the rate of deflection. It was determined that the optimum solution would be Farrat’s H2 Hybrid Bearings made up of 2 natural rubber layers with a stainless steel inter leaf plate, laminated along its centre line. In some cases, where horizontal displacements where high, the bearings were manufactured as slide bearings, incorporating an additional PTFE face on the upper surface, which would slide against another PTFE surface connected to the underside of the cell. Farrat’s Hybrid bearing system allows a high level of flexibility as they are moulded as a 1000 x 500 mm sheets, from which a variety of sizes can be cut.
Following QC checks, the bearings were individually labelled with a numerical code referencing where they should be placed in line with the architect’s drawings, and then delivered in a ‘Just-in-Time’ system to avoid a build-up of stock on site. On-site testing post-installation, has demonstrated that all performance requirements were achieved.
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