Foster and Partners and Ove Arup & Partners were warned as far back as February 1998 that the Millennium Bridge might require reinforcement to make it safe and to counter vibrations.
The now defunct Royal Fine Arts Commission predicted trouble for the £18.2 million crossing in its design review report and bridge specialists said then they were not sure how the structure worked.
Its report stated: 'The commission is concerned that there may be pressure to produce a more substantial structure or more elaborate railings and balustrading to deal with any perceived sense of insecurity to pedestrians from the height of the bridge or the vibration likely to be expected.' The bridge was closed just 48 hours after it began twisting and swaying at its opening on 10 June when 100,000 people made the crossing in just 10 hours.
Edmund Hollinghurst bridge specialist and managing director of consulting engineers Gifford & Partners, was at the design review meeting and noticed that the bridge showed obvious frailties.
'I've always been nervous about vibration and it was something that had to be addressed, ' Hollinghurst said. 'It looked like dampeners might seem appropriate.' However, Hollinghurst stressed his support for the bridge and described it as 'an exciting design'.
But embarrassment over the bridge's problems for the designers increased further last week when a rival engineering firm was called in to help diagnose the problem. Ove Arup appointed Flint & Neill Partnership, a consulting engineer specialising in bridge building, the day the bridge closed.
'They have not had bridge people working on the design, ' said Flint & Neill partner Ian Firth, who worked on the Wilkinson Eyredesigned bridge at Lock Meadow, Maidstone. He also said there is 'extraordinarily' low-level dampening on the bridge, which means that once the suspension cables start vibrating it takes a long time for the bridge to become steady again.
Ove Arup has been testing the bridge by sending groups of around 30 engineers over it to simulate crowds, shipping in a machine from the Building Research Establishment to simulate movement and applying shocks to cables. Arup chairman Bob Emmerson said the analysis could take at least a month.
The engineers are looking at a series of options to steady the bridge: stiffening the walkway so it acts structurally to stabilise the bridge; changing its frequency so it is less responsive to pedestrian traffic; and dampening vibrations by suspending counterweights from the southern end.