Engineers to mimic the human spine in construction of resilient bridge pier

A durable, low-maintenance and low-carbon bridge pier inspired by the anatomy of the human spine is being developed in the UK.

The bridge pier, which could be built in just one or two days and easily demounted at the end of its useful life, is being developed by researchers at Southampton University with funding from EPSRC. In use, it will be designed to withstand earthquakes and damage caused by traffic and cold weather.

Existing bridges, particularly those in colder countries such as the UK, US, Canada and Japan, suffer from corrosion caused by salt spreading during the winter months, meaning they require expensive maintenance, according to project leader Dr Mehdi Kashani.

“What’s more, when these bridges are under dynamic loading, either from a high-speed train or an earthquake, because of the fixed way they are constructed they tend to crack, and when concrete cracks it accelerates the deterioration,” said Kashani.

The human spine, in contrast, is made up of a number of vertebrae that are not fixed together, but are stacked flexibly on top of each other and so are free to move.

Between the vertebrae are intervertebral discs, which dissipate energy from the movement of the body and absorb and transmit forces without damaging the vertebrae, said Kashani.

“The vertebrae rock on top of the intervertebral discs, and the discs act as shock absorbers,” he said.

The new bridge pier will be based around precast composite segments without any reinforcing steel, designed to act as the vertebrae. In between these solid segments will be “intervertebral discs”, constructed from a new smart composite material being developed by the team, which will prevent the vertebrae from rubbing against each other, transfer shear forces through friction, absorb impacts caused by the rocking of the vertebrae, and provide mechanical damping under dynamic loading.

Unlike conventional composites formed of layers, which can delaminate, the new material will consist of entangled polymer fibres. Entangled materials based on titanium or metal alloys are already used in aerospace for vibration damping, said Kashani.

“We want to come up with something similar but using a polymer base,” he said.

The vertebrae and discs will be tied together using a pre-tensioned un-bonded composite “tendon”, designed to act like the spine’s longitudinal ligament, by pulling the piers back into their central position if the bridge is subjected to lateral forces from an earthquake, for example.

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