Humming bridges

Bridges are more complicated than they look

Bridges are more complicated than they look

There was a time when materials were the facilitating aspect of the design of any product. A bridge would be built, and it would be built from steel, for example. Fast forward to today and its surprisingly or unsurprisingly the other way around. In essence, everything that made a bridge difficult to design, (we’re talking safety, structural integrity and all that) is now taken care of by the steel, and all we have to do is put the thing together.

How, you ask?

Smart steel is just one example of a new generation of smart components and structures that can report when they may have suffered mechanical damage or corrosion. Sensors designed to achieve this may soon be built into buildings, bridges and a slew of other products, from cars and planes to body armour, so that crucial components can be replaced before they fail and cause damage to other infrastructure, and more importantly, other humans.

The vast majority of the bridges and other such structures that exist are old, and with age comes deterioration, just like us humans. Just look at the 2016 Vivekananda Flyover Bridge collapse in Kolkata, India, a fatal incident, causing 27 deaths and a further 80 injuries. This famed bridge, a seemingly perpetual hunk of steel girders was the last thing anyone in Kolkata would have expected to collapse, yet it did, with dire consequences.

Human inspectors certify bridges every two years, but they can miss small cracks, problems in hard-to-access locations. To make this certification process more dependable, scientists at the National Institute of Standards and Technology's Technology Innovation Program (NISTTIP) have developed piezo-electric sensors, embedded in the material used to make the bridge itself, that actively probe for faults in bridges, and, well, hum.

Just as ultrasound scanners use acoustic signals to image internal organs, these clever piezoelectric sensors can send acoustic signals into a bridge's interior. By listening for the returned signal, it can detect structural faults such as hairline cracks or areas of unusual strain, and let off a deep hum that alerts scientists that something’s gone wrong.

It seems quite underwhelming, perhaps even unnecessary for such a thing to exist, but its importance is not to be belittled. Call me crazy but have people not realized the changing climate patterns, particularly regarding natural disasters? When that massive tsunami is inevitably hurtling towards us, threatening the lives of everyone living nearshore, these little piezoelectric sensors woven into our coastal defenses might be the entity that prevents destruction. Nah, that was slightly exaggerated, but you get the point?

Essentially, what’s so revolutionary about this is not the integration of piezo-electricity based sensors right now, but what that means for the designs of the future. Further application with other smart materials can pave the way for an infinitely safer metropolis, where our structures are not just stronger and safer, but responsive to their present condition.

So, the next time you’re passing by and you notice a low humming sound coming from above, you know what’s up.