The Millennium footbridge in London gave engineers pause for thought when it was found to have a natural frequency close to that of human walking. This caused the bridge to move in response to people’s steps, which, in turn, caused people to synchronise their gaits, exacerbating the problem.
Big dampers have since been affixed at significant cost.
In order to allow architects to do their usual pushing the envelope, today’s invention aims to reduce the sensitivity of narrow bridges to the energy inputs from feet.
A version of this type of energy absorbing surface could be developed that extracted a larger fraction of energy from walking (using heavier, small-scale dampers). This would reduce the energy available for unfortunate bridge vibration (and slow walking speeds too).
Areas of the surface which made bigger contributions to bridge movement could be identified and programmed to have stiffer dampers.