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Issue 2 |
The full title of the lecture, "In pursuit of creative synergy - from the Sydney Opera House to the London Millennium Bridge", gives an idea of its very broad scope. Tony took us on a journey through his long and varied career as a structural engineer, bringing out the excitement of working on the design of some of the world's great buildings, and the constant need for creative interaction between professionals from different disciplines to solve new problems. Arup are, of course, particularly noted for their excellent working relationships with architects which have been key to the creation of many world-famous, landmark structures - the Sydney Opera House, Pompidou Centre in Paris and Hong Kong and Shanghai Bank headquarters in Hong Kong to name just a few.
Of course, no presentation concerning notable Arup projects would be complete without an account of the London Millennium Bridge. This footbridge, designed by Arup and architect Foster Associates, became infamous when it had to be closed only days after opening due to worrying levels of sway vibration caused by crowds crossing the bridge. In the weeks that followed, Arup engineers found themselves inundated by "helpful suggestions" of the cause from engineers around the world, mostly related to the bridge's unusual structural form. Arup kept an open mind and invested in some fundamental research. The cause was eventually identified as the previously little-known phenomenon of synchronous lateral excitation - essentially, when a low-frequency lateral vibration is set up, pedestrians find that the only way they can keep their balance is to walk at the sway frequency of the structure. A vicious circle is thus created, in which the pedestrians' involuntary response to the vibration actually reinforces it, until it reaches potentially dangerous levels. Having identified the cause, Arup were able to argue convincingly that the structural form was not a key factor, to design remedial works and to emerge with their reputation intact.
With structural engineering having such a long history, it is sometimes claimed that there are no major challenges left to overcome. On the contrary, this fascinating talk showed that each new structure still presents a novel set of problems and that creativity and innovation will play key roles in the structural engineering profession for many years to come.
The main lecture was preceded by two research-in-progress talks on Civil Engineering topics:
Martin Williams on "Structural Vibrations"
Chris Martin on "Numerical modelling of soil/structure interaction - conflicts and compromises"
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