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.
A bit like using lime mortar then?
No. Lime mortar is not flexible and hardens over time as it absorbs CO2 and reverts to limestone. It’s great advantage is that it is porous and wicks out and releases to the atmosphere the salts and moisture drawn up through ancient walls with no damp proof course. Sealing the moisture in using cement based pointing or plastering leads to corrosion of the stonework round the pointing and higher levels of damp in walls to the height of the top of the plastering.
Maybe a use for re-cycled plastics for the “intervertebral discs” & as corrosion resistant reinforcing in the precast composite ‘ vertebrae’.
Very interesting & simple concept which Nature has gifted us to take fare of all type of forces ( tensile,compression, Shear or Bending Moments static or dynamic ) during our life span unimaginable recurrences. Kudos to Dr Kashani’s team.
KM: new smart composite developed by team will prevent rubbing to transfer shear as friction and absorb impacts by rocking and provide dynamic damping _ new material consist of entangled polymer fibres like alloys used in aerospace :: sellership spikes scholarship again as such stuff is already abundant in compliant claddings spawned from coldwar closure campaigns in subsea stealthing inspired by intelligent insight like all best inventions ever since enlightenment, here in seemingly short supply given lifetime limitations never mind cost compared with compression concrete blocks infilled with rubberised relaxers _ indeed compliant concrete even was evolved as 70s soviet submarine stealthing skeleton! But who cares about established expertise in our emptyhead era of instant inspiration driven by dendragonry.
“….of entangled polymer fibres. Entangled materials based on titanium or metal alloys are already used in aerospace for vibration damping,” [and that of textile rotating spindles when out of balance!]
And the original thinking for this was based upon that well known researcher S Erin Dipity: who noticed the absorbance effect of domestic pan scourers (the metal ones!) and applied such to multi-directional forces causing vibration. Not my idea but that of a colleague.
How amazing that technology mimics mother nature and surprisingly comes up with a good/great idea yet again. I like the idea that waste plastic could be utilised in these types of structure rather than polluting our oceans.
Let’s hope it wasn’t a politician’s spine………………….
Surely the thing to stress here is the lack of steel in the design making it less susceptible to salt corrosion..?