• Transport and infrastructure

Christmas held in suspension

Strainstall's swift response in support of bridge operator Amey was crucial to the re-opening of the Forth Road Bridge two weeks ahead of schedule and just in time for Christmas.

There was considerable upheaval in the Scottish transport system on 4 December last year when engineers spotted a crack in one of the supporting structures of the Forth Road Bridge (FRB) and took the decision to close the bridge to all traffic until it could be repaired. This left commuters, hauliers and holidaymakers facing little prospect of the bridge being re-opened for many weeks.

Within days of the bridge's closure, its operators, Amy, contacted the Strainstall team which was busy working on configuring a sophisticated structural management system, BridgeWatch, for the soon-to-be-built Queensferry Crossing nearby.

Strainstall's systems technical authority, Andrew Scullion, explains;

'We are renowned globally for our expertise in bridge monitoring and testing services. Amey had a critical  issue and contacted Strainstall straight away. As industry leaders in structural health monitoring, we were able to provide specialist support in record time, utilising our state-of-the-art solution, BridgeWatch.'

After receiving the call, Strainstall's site project engineer, Dr Campbell McKee sacrificed his holiday to inspect the damage to the FRB at once and immediately formed emergency teams onsite with Andrew, while Paul Faulkner, product manager, started work with a team of eight technicians and engineers back at the company's operations bases to design a solution.

Project manager, Iain Salter, says;

'Within a day of that initial meeting we had a team designing, preparing and building hardware for the bridge, and also a team onsite beginning preparations for the installation of the sensors. Both teams immediately knew what needed to be done and were able to respond extremely quickly to Amey's continually-developing requirements.'

By rapidly installing a number of sensors to measure strain, temperature and tilt, the system delivered crucial monitoring and engineering information to support Amey's planned testing schedule and help ensure the bridge was re-opened without delay.

This was a high pressure job in the face of substantial traffic disruption but BridgeWatch enabled Strainstall to create and implement a specific monitoring solution which helped reduce the impact of the bridge's closure.

'The guys on site worked extremely hard in bad weather and difficult-to-reach locations to get things done in time for a load test, so the bridge could be open for cars just before Christmas,' says Andrew. 'They did a fantastic job, sometimes working right through the night.'

The bridge re-opened on 23 December - two weeks ahead of schedule. Amey's account director for the Forth Road Bridge, Mark Arndt, commented;

'The BridgeWatch technology provided finite detail on the structural behaviour of the bridge and was instrumental in enabling us to recommend opening the bridge to 90% of all traffic.'

From this initial 'crisis management' scenario, the BridgeWatch system's involvement has grown. Because the original fracture which led to the bridge being shut had been caused by fatigue failure, Amey was keen to assess how far down the fatigue cycle of the 50 year bridge the remaining non-failed elements were and how traffic load would affect them.

Rob Butler, managing director of Testconsult, Strainstall's sister company, said;

'The team's response was remarkable, given that typically it can take months to design, build and install a full structural health system - we managed it in days. BridgeWatch really does have the potential to transform the management of infrastructure assets, and there will come a time when every bridge and critical structure has a sophisticated preventative maintenance system like this to help properly assess and predict maintenance strategies.'

How BridgeWatch helped re-open the Forth Bridge:

• BridgeWatch brings together a highly sophisticated toolbox of sensors, data acquisition equipment and Strainstall's Smart Asset Management (SAM) software, to provide constant smart data monitoring in real-time
• When the Forth Road Bridge was closed, the Strainstall team installed monitoring devices around the fracture site to assess the likely impact of the damage, and the strength of subsequent repairs
• The team installed monitors on the other three corners of the bridge to assess when the bridge could be re-opened to traffic
• BridgeWatch helps engineers decide action required for the proposed next level of repairs, by tracking the stresses, strains and movements of the bridge against wind speed
• BridgeWatch is being built into the Queensferry Crossing and will be operated and controlled seamlessly on both bridges from one control room

Find out more about how Strainstall supported the Forth Road Bridge repairs:

• New Civil Engineer article featuring Strainstall: Fracture surgery | Forth Road bridge repairs