Metal fatigue can take down steel bridges. Scott Walbridge keeps them standing.
Bridges are stressed repeatedly as trucks and other heavy loads pass over them. The effect is small – but can add up to critical damage. “Think of bending a paperclip back and forth,” says Scott. “You can only bend it so many times before it breaks.”
Bridges don’t usually snap in two, but they do develop cracks at the points of maximum strain: the welds.
Scott discovered that peening the welds – that is, hammering them to create many small dents – can reduce this cracking dramatically. His work with tubular steel bridges showed that peening can double the service life of the bridge. Results are even better if the welds are treated after the bridge is erected.
Tubular steel bridges might be the bridge of the future, but Scott is eager to apply his technique to the bridges of the past: plate-girder bridges. Built in the post-war boom, many of these bridges are coming to the end of their usability. Scott thinks his rehabilitation techniques could prolong their life and help distribute the cost of rebuilding them over time.