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FIBRE PROVIDER

PILING AND FOUNDATIONS

Disruptive magnetic interference means glass fibre reinforced plastic is being used in concrete piles at a new research facility in Liverpool. Damon Schünmann reports.

Magneto would not be impressed.

The X-men super bad guy would be rendered powerless by the lack of metal on entering the new NMR (Nuclear Magnetic Resonance) unit at the University of Liverpool in north west England. This would be partly because the piles installed to support the new facility were built without metal reinforcement, as conventional mild steel - strictly prohibited, would interfere with magnetic fields and corrupt readings.

'Once it's finished it can't have any ferrous metal at all near the NMR unit so we have asked the guys to be very careful that nothing drops in the holes that could fry the magnet, ' says Rock and Alluvium regional manager north, Rob Jenson.

Researchers will use the £1.75M NMR machine to analyse very highly detailed structures of proteins and other biological molecules. It will be used to help understand fundamental processes in cells and how proteins malfunction in disease.

'The original suggestion was to use stainless steel which isn't magnetic, ' says Rock and Alluvium construction technical manager, Steve Hadley. 'But it's [comparatively] heavy making it more dangerous for the personnel involved so health and safety was the primary consideration for choosing a different reinforcement material, glass fibre reinforced plastic [GFRP].'

He says it has similar strength and bond characteristics to mild steel, which being cheaper, is however being used in piles outside the sensitive zone.

But he explains that although there is a history of its use in ground engineering, such as sacrificial reinforcement for TBM launches, another reason for using it at the university is for the contractor to assess its potential for use on other projects.The piles have a factor of safety of three meaning load testing is not required and as they will only resist compression the reinforcement is nominal. But they were still integrity tested. However, GFRP reinforcement does have the structural capacity for tension and bending loads.

Hadley says that although GFRP has been used in the concrete framework surrounds of NMR facilities, he believes it has not been used for the piling in the UK.

Although both types of piles are 350mm diameter, the non-metallic pile cages needed to be square.

'Because we wanted 200mm cages we are using the GFRP in squares as our supplier, Hughes Brothers, couldn't provide rings at this diameter, ' says Hadley.

The company flew the U-shaped pieces in from Nebraska, and Jenson notes the material has been used on at least six or seven NMR facilities in the U.S. The rig crew put the piles in through fill material then clay and 1m into sandstone to give a 4.5m depth. Of the 70 CFA piles, 39 sitting below the NMR building's central area have GFRP reinforcement with a further 31 containing mild steel supporting parts of the structure either side. The two-and-a-half day job was completed at the end of July.

'With the rising cost of steel this may be a viable option on jobs where we would normally use steel, although at the moment GFRP is still more expensive, ' says Hadley.

Rock and Alluvium says the project is part of its ongoing growth in the north of England after it opened a Warrington office earlier this year.

Main contractor Wates Construction work on the building, an extension to the University's School of Biological Sciences, began in July and will complete early next year.

The £3.5M facility will open by February or March 2007.

The NMR (Nuclear Magnetic Resonance) facility 'The centre will be used to examine the very fine detailed structure of proteins and their interactions with small molecules with a view to identifying new medicines, ' says Professor Steve Edwards of the University of Liverpool. 'There are a number of key projects looking into Alzheimer's, cancer and tropical diseases.

The work aims to identify small molecules that can interact with proteins to block their function. If a protein is involved with cancer, blocking its function with a small molecule could prevent cancer cells from growing.

'It's a magnet that acts as a spectrometer measuring the electrical fields of the components that make up proteins, ' says Edwards. 'So ferrous metals can't be used [in construction] as anything that generates or interferes with a magnetic field would interfere with readings.'

The measurements are made at about -80 oC, as the cooler the instruments are, the less background interference there is.

Edwards says the NMR facility will be one of the few in the country that will be able to make both types of readings in this field of research.

One is measuring the properties of proteins in solution while the other is looking at the properties of proteins in a solid state.

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