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Testing times

Spotlight Structura testin - New clients and new challenges face the structural testing and inspection sector.NCE reports.

Two forces for change are hitting the market for structural testing and inspection services simultaneously. The balance of work is shifting from inspection of highway structures to structural investigation of buildings. At the same time traditional inspection techniques are giving way to high-tech, non-intrusive solutions including remote monitoring systems.

Gareth Jones is a director of consultant Stats, which offers remediation design services as well as inspection and testing.

He says the reasons for the shift in focus from highways to buildings include the completion of the Highways Agency's 15-year rehabilitation and bridge assessment programmes, and an upsurge in refurbishment and alteration of existing buildings.

Innovative non-destructive inspection techniques which are finding favour include thermographic surveying to detect water leakage and heat loss, radar scanning for slab thickness, reinforcement layout to find voids, and ultrasonics to detect cracking and porosity.

Jones reports increasing demand for state-of-the-art cover meters to detect reinforcing bars up to 200mm deep. Enquiries about remote datalogging systems are becoming more common.

Another specialist, Testconsult, was set up 20 years ago to use innovative techniques such as ultrasound for pile integrity testing. Director Simon French says: 'Remote instrumentation and monitoring is at the heart of Testconsult's reason for being.'

Now it is increasingly involved in installing instrumentation for bridge monitoring, either as a routine measure or because of a one-off event such as an abnormal load.

A typical current project involved instrumenting a bridge with tilt sensors and strain gauges to monitor its behaviour when it carried a 400t transformer en route to a nearby power station.

A datalogger automatically sends readings to the company's website, where it can be inspected in real time by anyone in possession of the appropriate password. Ultimately the information gathered will be used to validate and refine finite element design models, says French.

Another recent project involved casting corrosion probes into a bridge deck. By measuring the electrical potential of the deck reinforcement, the onset of corrosion can be identified and warnings sent out.

Maintenance efforts can then be targeted more effectively.

Research and testing organisation Ceram undertakes both on-site testing and performance testing for new products and building systems, often on behalf of the British Board of Agrement (BBA). Regarding product evaluation, Geoff Edgells, manager of the building technology division, reports 'a big increase in interest in prefabricated walling systems'.

This emanates from the Egan Report and subsequently a Housing Corporation stipulation that 25% of housing association properties must be built by 'modern methods', he says.

Two groups are interested:

'One is manufacturers who might have a customer such as a supermarket chain which wants to be satisfied the system is suitable and fit for the purpose.'

The other group consists of companies seeking BBA certification for systems they want to make available generally. Ceram has itself led the development of a new brick walling system, Traditional Plus (see box).

As for on-site work, Edgells adds: 'We're doing a lot of testing connected to changes of use of buildings, often historic or listed.'

For this sort of work Ceram has been making use of a technique it developed to help predict the behaviour of the Victorian brick viaducts at Waterloo during tunnelling for the Jubilee Line Extension.

This involved taking extra large 300mm diameter cores from the arches, load testing the cores and correlating the results with laboratory research on similar masonry.

Such techniques were used in the Victorian Round Foundry in Leeds, which is being redeveloped as the heart of an 'urban village' and e-commerce centre.

Assessment of the strength and condition of key features, such as a brick arch floor, was needed to decide whether they could be retained.

Ceram also carries out direct measurement of the strength of floors by monitoring deflections while loading the floor with bags containing water or gravel.

This is usually to find out whether the floor is capable of withstanding increased loading due to a change of use.

At the Kelvingrove Art Gallery and Museum in Glasgow, curators wanted to put more artefacts on display. Ceram was called in to test a floor built in the 1890s using the Hennibique system, a precursor to modern reinforced concrete. The floor in question passed the test, despite a concrete strength of only 5N/mm

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