Why did the London Millennium Bridge 'wobble'?

December 16, 2008

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 looking at how humans stay balanced while walking.

The same pedestrian-structure interaction 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 behaviour of the pedestrians. 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.

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."

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.

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.
-end-


University of Bristol

Related Walking Articles from Brightsurf:

Why walking to work may be better for you than a casual stroll
Walking with a purpose -- especially walking to get to work -- makes people walk faster and consider themselves to be healthier, a new study has found.

Spinal cord gives bio-bots walking rhythm
Miniature biological robots are making greater strides than ever, thanks to the spinal cord directing their steps.

These feet were made for walking
Many of us take our feet for granted, but they have a challenging job in the biomechanics department.

Walking sharks discovered in the tropics
Four new species of tropical sharks that use their fins to walk are causing a stir in waters off northern Australia and New Guinea.

Micro implants could restore standing and walking
Researchers at the University of Alberta are focused on restoring lower-body function after severe spinal injuries using a tiny spinal implant.

Walking changes vision
When people walk around, they process visual information differently than at rest: the peripheral visual field shows enhanced processing.

Virtual walking system for re-experiencing the journey of another person
Virtual-reality researchers have developed a virtual-walking system that records a person's walking and re-plays it with vision and foot vibrations.

A large study indicates how cities can promote walking for travel
Coinciding with the European Mobility Week, a study performed in seven European cities focuses on walking for travel, a strategy to increase physical activity in cities.

Robotic cane shown to improve stability in walking
By adding electronics and computation technology to a simple cane that has been around since ancient times, Columbia Engineering researchers have transformed it into a 21st century robotic device that can provide light-touch assistance in walking to the aged and others with impaired mobility.

Water walking -- The new mode of rock skipping
Utah State University's Splash Lab not only reveals the physics of how elastic spheres interact with water, but it also lays the foundation for the future design of water-walking drones.

Read More: Walking News and Walking Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.