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Scottish bridge hit by connector test delays

Clyde Arc contractor Nuttall was this week facing delays to the construction of Forthside footbridge in Stirling, as testing on the Macalloy connections has slowed progress.

Components on the Forthside bridge are standard Macalloy connectors, unlike the bespoke products which failed on Glasgow's Clyde Arc.

On the Arc, one bespoke connector suffered a clean break across its connection lugs and another was found to have a crack in the same place (NCE 31 January).

A Nuttall spokesman confirmed that components for the Forthside railway footbridge which spans seven rail tracks, were being tested.

"The project specification required a level of testing not included in the supplier's standard," he said.

"The components were brought to site without the testing being done. I couldn't say about the results of the test or comment on the relation of it to the Clyde Arc. The bridge deck is currently in place over Stirling station and we are currently waiting for resolution and return of the components to site to allow for the tensioning of the struts. We are somewhat in limbo at the moment."

Forthside's Macalloy connectors are undergoing non-destructive testing, something that project consultant Gifford says is standard on all critical steelwork components.

This testing regime comprises ultrasonic tests and magnetic particle inspection tests to get a feel for the nature of the material, its homogeneousness and whether there are any flaws or inclusions.

The tests are normally carried out by the steelwork supplier.

Rowecord, which is fabricating the steel for the project, declined to comment and Macalloy was unavailable for comment.

Investigations into why the Clyde Arc connection failed are now complete.

But the design and construction team has chosen not to publish the findings of why the connection failed, leaving other engineers and clients to speculate on what happened.

"Network Rail and our client [Stirling Council] are waiting to see what the outcome is [of the investigations into the Clyde Arc failure]," said Gifford associate Steve Thompson.

"How can we give [our client] confidence if we haven't seen the report?"

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