Structural monitoring could have identified Forth Road Bridge fault that led to 2015 closure

Structural health monitoring systems (SHMS) could have stopped the truss end link failure that closed the Forth Road Bridge for three weeks in 2015.

One of the truss end links connecting the bridge to the north east main tower failed as a result of a seized pin in December 2015.

SHMS are now being used on the Queensferry Crossing, and Bear Scotland unit bridges manager Chris Tracey told NCE’s Future of Bridges conference that the technology could have alerted teams to the Forth Road Bridge fault before the failure.

“With the benefit of hindsight we believe that if there had been some form of SHMS installed at the links at that time [the seized pin] may well have been picked up before failure,” he said.

“It was a hidden defect – the bridge was moving and performing as it normally would and there was nothing visible to indicate that there was something untoward – but over time due to the increased stresses in the link as the pin wasn’t rotating, the link itself failed.”

The Queensferry Crossing was completed in 2017, after the discovery of the Forth Road Bridge’s fractured truss-end link in 2015. It now carries the 100,000 vehicles a day which were using the Forth Road Bridge, leaving the older structure to carry buses, pedestrians and cyclists.

Following the 2015 event, Transport Scotland invested in monitoring and analytics on both bridges to provide more information on their health and avoid similar failures.

Tracey emphasised the benefits of investing in these systems from the start of projects.

“The Queensferry Crossing is a critical piece of infrastructure in Scotland,” he said. “It’s incumbent on us to make sure we minimise disruption from our activities. This was considered early on in the design stage by Transport Scotland and the delivery team of Jacobs and Arup and they decided to implement a SHMS.”

In planning the project, Transport Scotland looked at bridge design around the world with a particular focus on Hong Kong and some of the large bridges there.

“These structures were all getting the SHMS fully implemented at the design and construction stage,” Tracey said.

“These systems allow alarms to be generated during extreme events and automatically generate integrity reports following extreme events as well as annual performance monitoring and service life reports.”

Source https://www.newcivilengineer.com/latest/structural-monitoring-could-have-identified-forth-road-bridge-fault-that-led-to-2015-closure-30-06-2021/

Department of Civil Engineering https://www.ibu.edu.ba/department-of-civil-engineering/