Surely mine were not the only eyebrows to elevate on reading the latest Fitzpatrick and colleagues' comment on the wobbly bridge (NCE 7 June).
They maintain that 'the sway problem on the Millennium Bridge had nothing to do with the crossing's ground breaking design'.
However, their comments appear to contradict this statement by blaming a combination of pedestrian density and a lateral frequency below 1.3Hz. Problems that followed were then attributed to a lack of knowledge of this damaging lateral excitation during the design period.
To its credit, Arup has initiated research and synchronous lateral excitation is now better understood and will no doubt generate future guidelines. But as I pointed out at the ICE Millennium Bridge meeting on 26 April, the International Association for Bridge & Structural Engineering's (IABSE) 1987 book Vibrations in Structures covers this form of vibration.
The apparent lesson is that designers, particularly those involved with innovative structures, need readily available information on all previously recorded structural failures. With modern technology, this would seem entirely realisable.
Brian Pritchard (F), Member of Executive Committee, IABSE British Group, Lindfield, West Sussex