When   Monday, February 16, 2009   Time   4:00 PM - 5:00 PM  
Where   Technological Instit M 416 2145 Sheridan Rd.   map it
Audience   - Faculty/Staff - Student - Public
Contact   Molly E Scanlon   +1 847 491 5586  
Group   McCormick-Colloquia Engineering Sciences and Applied Mathematics

Applied Math Colloquium

Title: Synchronous Lateral Excitation on London's Millennium Bridge

Speaker: Daniel Abrams, Massachusetts Institute of Technology

Abstract:

On June 10, 2000, London's new footbridge across the Thames opened to great acclaim. Within 48 hours authorities were forced to close the bridge, citing a dangerous lateral vibration induced by the large crowds. After 20 months and £5 million in modifications to increase damping, the bridge reopened, but the origin of the problem remained a mystery.

Together with Prof. Steven Strogatz and Prof. Allan McRobie, I devised a model of human-structure interaction to explain the pedestrian-driven wobble. Borrowing techniques from mathematical biology, we model human walkers as limit-cycle oscillators that are weakly coupled to lateral motion of the bridge deck. Our model predicts spontaneous outbreaks of synchronization among the walkers and the rapid onset of large-amplitude vibrations beyond a threshold number of walkers. This prediction closely matches video footage of opening day and explains results of experiments conducted while the bridge was closed.