Bridging the gap: New methods of structural assessment
Every year hundreds of millions of pounds are spent unnecessarily demolishing or strengthening bridges that do not pass current methods of structural assessment.
The Department of Architecture and Civil Engineering are working with the Highways Agency and Network Rail to develop better methods of assessing the structural quality of bridges. The research will not only help to save bridges, but also save public money and prevent disruption to businesses and commuters.
“Without the findings of Bath's research, these structures would have needed very expensive replacement or strengthening works amounting to hundreds of thousands of pounds.”
Jon Shave, Parsons Brinckerhoff
Using existing methods of assessment, many older bridges are condemned to demolition, despite their ability to withstand the loads of today’s heavy traffic. These older bridges were often built to standards that are considered inadequate nowadays, such as insufficient anchorage of internal steel reinforcement.
Developing new methods of assessment
Dr Antony Darby and Professor Tim Ibell from the Department of Architecture and Civil Engineering carried out tests to prove that an older bridge can still carry a normal load, regardless of whether the bridge reinforcement is anchored or not. By considering how structural behaviour changes as a bridge is loaded, it can be shown to be capable of carrying its load safely.
The Highways Agency has adopted this new assessment process, which does not condemn bridges purely because of the way they are reinforced. The research received a prestigious award from the Federation Internationale du Beton (the International Federation for Structural Concrete).
Introducing a new way of strengthening bridges
The team have also developed an award-winning method for strengthening bridges with inadequate capacity. The method, known as deep embedment strengthening, use holes drilled into the beams of the bridge, which are then filled with fibre reinforced polymer (FRP) bars.
The method is ideal for bridges where the sides of beams are inaccessible, preventing the use of conventional strengthening methods. Deep embedment strengthening is also significantly more efficient than standard methods due to the way the bridge is reinforced.
The research was awarded the Institution of Civil Engineers’ Bill Curtin Medal.
Thanks to their success in developing a new method of strengthening bridges, the team have been asked by the Concrete Society to take the lead in revising the UK’s guidance policy on strengthening concrete structures.
The techniques developed for dealing with inadequately reinforced bridges have also been incorporated into a draft Highways Agency Bridge Design Document, used by consultants during bridge assessment.