Research in Focus

Why bridges fail

With 30,000 bridges on the UK rail network, many dating from the late 1800s, monitoring damage and predicting end of life is an expensive and challenging business. Researchers in our Department of Civil and Environmental Engineering are working on some innovative physical and virtual solutions. 

Finding the clues in legacy bridges

The majority of metallic railway bridges in the UK – approximately 10,000 in total – are already over 100 years old and therefore potentially approaching the end of their life.  

Replacing these bridges will not only be extremely expensive but also practically impossible unless phased-in over many decades. Identifying the likelihood of a bridge’s failure, therefore, will be vital in order to make effective use of limited resources while avoiding unnecessary disruption of the network. 

A current project with Network Rail and Mott MacDonald has involved bringing an entire bridge onto Manor Park campus for a deep analysis in order to better understand fatigue and corrosion of different materials and assembly methods. The decommissioned bridge, originally located south of Glastonbury and believed to date from around 1870, has been dismantled and separate pieces brought into the lab for testing. 

Understanding fatigue in these bridges, constructed in the late 19^th and early 20^th centuries, is particularly challenging because they are not built to a standard design. 

Dr Boulent Imam is leading the project. He says: “These bridges are made from materials which are no longer used for bridges such as wrought iron. They are also ageing differently depending on factors such as their location. Those close to a coastline have been very badly affected by the saltiness and humidity. Others near ports have experienced heavy loads in the past. 

“Physical testing is indispensable in understanding the condition of these bridges. The holy grail – and what we are aiming to achieve eventually through modelling and analysing monitoring data – is to create a ‘digital twin’ of the infrastructure. This means we would have on the computer every different type of bridge in its current condition which we could then virtually subject to stress and load analysis.” 

Fighting natural disasters with natural solutions 

Global warming is causing the two extremes of flood and drought, but researchers in Surrey’s Global Centre for Clean Air Research (GCARE) are helping to combat these hazards through natural solutions – with a particular focus on vulnerable communities. 

Nature-based solutions involve activities such as protecting, restoring and improving natural habitats, and implementing new solutions (eg. planting specific types of vegetation) in order to combat societal challenges such as flood, landslides, heatwaves, drought and coastal erosion risks. The GCARE team was recently part of the four-year OPERANDUM project – involving 26 international partners from seven European and three non-European countries – which successfully demonstrated the benefits these solutions can bring in 10 open air laboratories. 

Dr Sisay Debele, research fellow at GCARE, explains: “Having implemented solutions in our open-air laboratories in locations around Europe and elsewhere, we are now evaluating these solutions using numerical models and remote sensing (airborne or satellite) techniques, with promising results. In our open-air laboratory in Greece, the use of natural water retention measures and the restoration of an existing natural water retention measure which acts as the best solution to reduce flood and drought risks have proved to be effective. In Germany there’s been a reduction in flooding risk due to the replacement of mixed (riparian) forest with pasture land (animal grazing).” 

Now the GCARE team is turning its attention to the ‘forgotten cities’ of England, Scotland and Wales which need the most support in adapting to climate change. The Centre is leading the UKRI-funded RECLAIM Network Plus for vulnerable and deprived smaller towns and cities. Typically, these areas lack funding or political visibility, so the network will act as a ‘one-stop shop’ to enable them to access all the information and support they need to install green and blue infrastructure. 

Professor Prashant Kumar, founding director of the GCARE, says: “People living in deprived areas tend to suffer the most from air pollution and summer heatwaves, and don’t always have access to safe green areas near their homes. These cities want to create nature-based solutions like green roofs but don’t know where to start.”