World-first for new tensioned membrane mesh gives £140m Energy Recovery Facility the perfect cover
“Base Structures found a technical solution on the basis of their knowledge, creativity and problem solving attitude. They transferred successfully the information from design study onto the final construction.”
Andreas Clausen, HOCHTIEF Construction Manager
The team
Philippe Quetteville, Architect, S’PACEJan Felgendreher, Project Manager, HOCHTIEF
Andreas Clausen, Construction Manager, HOCHTIEF
Miles Nichol, Senior Project Manager, Veolia
Mark Smith, Head of Projects, Base Structures
Francis Buchanan, Project Manager, Base Structures
Project highlights
• World first application as tensioned membrane for new, high-porosity pvc coated polyester mesh with wire reinforcement strands incorporated in the fabric
• Material allows inflow of air for cooling purposes but provides visual shielding
• Cost effective solution
• Innovative fixing system offers exciting potential for further uses of new material
The background
Base Structures were asked to tender for the fitting of a screen to minimize and soften the industrial visual impact of the cooling section built at the rounded northern end of the new £140 million Energy Recovery Facility (ERF). When operational this new ERF will take receipt of some 210,000 tonnes of municipal solid waste each year, to be treated in two boilers. Power generated will run the plant with a net surplus of about 16.5 MW also being produced.
The brief
A futuristic looking superstructure has been designed by the French architects S’PACE to contain the 50 x 45 m x 27 m building. “The architectural shape of this plant gave us new challenges for the structural steel erection and cladding installation, which were professionally and successfully handled”, says HOCHTIEF Construction Manager Andreas Clausen. “The highly engineered cladding materials support the architectural vision”. The southern part of the building (Tipping Hall, Bunker Hall) has a metallic façade as it is covered with KALZIP, The Boiler Hall and the southern end wall are clad with lightweight polycarbonate panels, DANPALON.
The challenge to Base Structures was to install a suitable screening for the air-cooled condenser area: a 54 m diameter half dome on the northern end of the Newhaven ERF which needed to obfuscate the harsh detail of the externally mounted cooling equipment. “We were asked to enter a two stage tender for the project,” said the company’s Project Manager, Francis Buchanan. “For the first design stage we had to provide a 2/3 model of one of the 48 trapezoidal bays to demonstrate that we could make the design work with the material the architects wanted to use.”
The material specified by the French architects was Serge Ferrari Stamisol FTD 752 – a new mesh fabric developed as a result of a close collaboration between S’PACE architect Philippe Quetteville and Ferrari development manager, Carlos Saiz and his team. Its porosity of 50 - 55% allows plenty of air into the Air Cool Condensers for ventilation purposes, however, its wide opened weaving configuration design provides sufficient material to generate the required screen effect.
However, it has never been used before as a tensioned membrane. The inherent flexibility of the fabric meant that it would need to be fitted in such a way that the daily stresses and strains imposed on these very large wind catching sails would dissipate uniformly into the enclosing skeletal steel frame.
The challenge
Ferrari Stamisol FTD 752 is a mix of 54 % galvanised steel wire, 38 % PV mesh and 8 % PVA. The metal content prevents welding the fabric together into sections. “The second challenge we faced,” said Project Manager Francis Buchanan, “was in fitting the material to the supporting steel structure in the normal way. Ordinarily we would provide a typical Kadar edge for insertion into the aluminium extrusion, and then apply the tension required. As this mesh is 50 % porous there was insufficient strength to attain the loads necessary folding the material back on itself (to create a pocket for Kadar), stitching and then using our tried and tested methods of installing using flat metal clamps.”
The solution
Innovative solutions were found to both problems, pointing a way forward to the new Ferrari Stamisol fabric being applied to many other structures across a wide range of applications.
“We hit upon the idea of a ‘wavy’ clamping system,” says Base Structures’ Head of Projects, Mark Smith, “using an aluminium extrusion which allowed us to pass the load evenly through the steel, rather than through the PVC. We made a series of different prototypes until we evolved a fully engineered design that achieved the loads necessary.”
Two different clamps were developed: an ‘intermediate’ design to hold the sections of fabric together, and a ‘perimeter’ design, used to clamp the joined sections to the supporting steel structure. The only modification necessary was to pre-stress the mesh before it was clamped in.
The installation
“The installation of heavy process equipment such as the air condensers within the northern end of the ERF plant had to be completed before the steelwork erection and the installation of the mesh. This sequence enabled commissioning of the plant to commence in spring 2011”, explains Andreas Clausen, HOCHTIEF Construction Manager.
Installation of the mesh above the heavy process equipment took around six weeks for a team of six on the ground fitting sections together and 14 riggers, clamping and bolting the sections into place. Having refined this techique, Base Structures is confident it will significantly reduce this build time for future projects.
The benefits
The traditional material to be used for an installation like this would have been PTFE, but that would not have offered all the benefits of porosity and it would have cost a lot more. Base Structures costs came in at just over £ 300,000 for a challenging installation rising to 27m, with a total coverage of 1,500 sqm across the 48 bays.
The material used also had a distinct ‘weave’ built into it, creating a pleasing visual effect which will shimmer in the light. The installation will keep looking good for many years.
“The final result provided the project with a cost effective solution and delivered the architects with the visual impact and technical integrity they wanted,” saidFrancis Buchanan. “Serge Ferrari are delighted that we have demonstrated how their product can be used in a range of very demanding applications… and it’s also another first in the world of tensioned membranes for Base Structures.”