When the original Forth Bridge was completed in 1889 it was heralded as a modern wonder of the world, a bridge of the like that had never been seen before. Its upkeep, however, would turn out to be never ending, leading to the well known phrase "it's like painting the Forth Bridge" (though in fact this is no longer the case, owing to modern painting techniques and products!).
With the opening, earlier this year, of the new Queensferry Crossing across the Forth estuary, running parallel to the original bridge, will this new bridge create similar headaches to maintain? It turns out that new technology comes to the rescue!
Sensors are embedded in the structure, such as small microphones on the cables, to detect changes to the bridge. These sensors, which also monitor the weather conditions and traffic levels, are connected to a computer system that knows their locations and can report back any faults that have been detected. This enables engineers to pinpoint any potential problem as soon as it occurs, enabling them to take action to prevent more serious damage occurring.
In turn, this improves the safety and efficiency that the bridge operates at, along with minimising the disruption caused by maintenance. Thus, while this monitoring will be performed endlessly, the maintenance of the Queensferry Crossing should be nowhere near as laborious as for the original Forth Bridge.
One of the biggest headaches for the engineers tasked with managing these pivotal transportation assets is knowing when and how to act. Traditionally it has been necessary to regularly inspect the structures. This is a dangerous, expensive and disruptive task. It is also incredibly difficult to assess the structural integrity of elements such as tendons buried deep inside a bundle of other tendons forming wires wound into cables supporting the road below.