Following best practice principles, our original design and analysis was carried out twice in Arup's by two totally independent teams. In addition to this an independent firm, Mott Macdonald , conducted their own separate analysis. The process of checking and double checking the design has now been repeated. The results of this review and comparison show that, apart from the unexpected movement, the bridge is reacting as predicted. In addition, we are in discussions with a number of academic experts and institutions, and have commissioned research from Imperial College and from Southampton University.
All suspension bridges move, sometimes imperceptibly.
The problem in this instance arises when the vibration caused by groups of people moving across the bridge tie in with the horizontal frequencies of the bridge, setting up a perceptible lateral movement. As the motion becomes more noticeable, people instinctively adjust their pace in time with the movement of the bridge in order to feel more stable. Understanding why it happened The structure of the bridge was designed in accordance with best practice, and all applicable codes and standards were not only met but exceeded. However these codes and standards do not address the movement that occurred at the opening of the bridge. As a result of the work we have done, and are continuing to do, the knowledge base of the industry will be expanded and future projects will be able to take account of these new measures and understandings in their designs.