On its opening day, the London Millennium Bridge experienced unexpected swaying due to the large number of people crossing it. A new study finally explains the Millennium Bridge 'wobble' by concluding that humans did not walk the way engineers would have preferred.
It has generally been thought the Millennium Bridge 'wobble' was due to pedestrians synchronizing their footsteps with the bridge motion. However, this is not supported by measurements of the phenomenon on other bridges.
Instead, it was the behavior of pedestrians and it has also been identified on several other bridges, including Bristol's famous Clifton Suspension Bridge. The phenomenon is not related to the structural form of the bridge, but rather the behavior of the people walking on it. The paper by civil engineers at the University of Bristol, published in the Royal Society journal Proceedings of the Royal Society A, examines the basic way humans maintain balance.
The most famous wobble in America: The Tacoma Narrows Bridge Collapse of 1940, though that one was resonance and not pesky people who chose not to walk the way engineers had designed the London Millenum Bridge to withstand.
Balance is achieved by changing the position of foot placement for each step, based only on the final displacement and speed of the centre of mass from the previous step. The same balance strategy as for normal walking on a stationary surface was applied to walking on a laterally swaying bridge.
Without altering their pacing frequency, averaged over a large number of cycles, the pedestrian can effectively act as a negative damper to the bridge motion, which may be at different frequency. Hence the pedestrian can inadvertently feed energy into bridge oscillations.
Dr John Macdonald, Senior Lecturer in Civil Engineering, said: "It is clear that the motion of the bridge affects the force from the pedestrian, rather than the pedestrian simply applying an external force."
The researchers found, to their surprise, that pedestrians walking randomly, keeping balance as normal can cause large bridge sway. This finally seems to explain the initiation of the Millennium Bridge 'wobble' and gives new insight for designing bridges to avoid vibration problems.
- PHYSICAL SCIENCES
- EARTH SCIENCES
- LIFE SCIENCES
- SOCIAL SCIENCES
Subscribe to the newsletter
Stay in touch with the scientific world!
Know Science And Want To Write?
- Artificial Intelligence: It's Time To Talk About What Emotions We Want AI To Have
- Lettuces Now, What Next - Could Astronauts Get All Their Oxygen And Food From Algae Or Plants?
- Brain Size Matters When It Comes To Remembering
- Innate GMO Potato Deregulated By USDA
- Most Idiotic Rejection Of Course From Philosopher Of Science Not Grasping Relativity
- An Historical Moment For Diabetes
- Alpha Lipoic Acid Dietary Supplement Slows Aging In Mice
- "The top spin is indeed being measured, with results in agreement with standard model predictions..."
- "Without a magnetic field on Mars, it should be patently obvious that terraforming attempts would..."
- "For instance would it be possible to measure the g-factor of the top quark? A dirac particle should..."
- "Dr. Federoff is wrong about golden rice being tied up in the regulatory process for more than a..."
- "Turbine operators have an inate drive to reduce all kinds of noise in their turbines - noise is..."
- Fish oil diet versus gut microbes
- Naps linked to reduced blood pressure and fewer medications
- Why girls are less interested in computer science: Classrooms are too 'geeky'
- Frogs make irrational choices - and what means for understanding animal mating
- Depression, blood pressure extremes predict highest rates of vascular events
Books By Writers Here