BridgeBot Could Save Millions in Bridge Repair Costs

Switzerland has lots of bridges. In fact it has 3,500 motorway bridges and thousands more on cantonal roads over the lakes, rivers and valleys for which it’s famous, many of which are constructed from reinforced concrete.

These bridges are often gritted with de-icing salts throughout the year because of icy and snowy weather. Over time the chloride ions from these salts corrode the concrete reinforcement in the structure and the damage can go undetected until it is visible to the naked eye. At which point, you may well need to empty a few Swiss bank accounts to cover the cost of the repairs.

With the potential to save millions in repair costs, a bridge crawling robot has been designed to access the difficult to reach spots on bridges and identify early signs of corrosion. The robot, called C2D2, in homage to its famous Star Wars counterpart R2-D2, can reach almost any part of a concrete structure, including notoriously difficult areas like the undersides of bridges thanks to its patented suction cup design.

Bernhard Elsener, a professor at the Institute for Building Materials at ETH Zurich, developed the technology to detect the onset of corrosion in reinforced concrete over 25 years ago. The problem was, actually getting engineers to the difficult to reach areas of these huge structures proved logistically challenging, time consuming and expensive. To solve this, Professor Elsener and a team of researchers from the Institute for Building Materials have developed and patented C2D2. This little robot gives access to the entire bridge, including the underside, while the engineers stay safely on the ground. The robot’s system uses an electrode attached to a wheel to measure electrical potential differences in the reinforced concrete as it moves about the structure. Large differences may mean that the reinforcement has already started to corrode in those areas. The data is transferred to a computer and then analysed. Professor Elsener explains:

“We analyse the half-cell potential map, checking for local minima and gradients. Statistical evaluation of the data helps in the interpretation, determining the potential values for passive and corroding reinforcement in concrete. A camera system on the ground follows the pink ball on the robot. This allows us to determine the position and then the x-y coordinates can be exactly calculated.”




The development team suggests that by mid-2015, C2D2 will have its own navigation system, instead of being operated manually and will be able to identify and overcome obstacles by itself. Researchers are also working on a software program that will allow C2D2 to interpret much of the data itself without being as reliant on a team of analysts on the ground. Professor Elsener added:


“C2D2 can help to create a safe and sustainable infrastructure at a relatively low cost – that was the motivation behind the project.”


C2D2 won an award in the ‘Prolongation of service life’ category in an international competition at the Concrete Innovation Conference (COIN) on 13th June 2014.


Images courtesy of ETH Zürich