How do you know when a suspension-bridge cable is about to fail? That's the question engineers at Columbia University in New York are trying to address in a new experiment.
Most suspension bridges share the same basic design: Giant cables strung between two towers are anchored to the shore on either side. The roadway hangs suspended below, with all its weight pulling on the main cables.
And these bridges are built to last; some of them are more than 100 years old, including New York City's Brooklyn Bridge. San Francisco's Golden Gate Bridge is more than 70 years old. But none of these bridges will last forever.
Cables — bundles of thousands of thick steel strands spun together — are typically visually inspected once or twice a year. But Columbia engineers are looking for a more systematic way to inspect cables — and, in the process, to predict a cable's life span.
So they are testing a system where tiny sensors are embedded inside the cable bundles to track the cable's condition round-the-clock.