httpwwwyoutubecomwatchvgQK21572oSU httpsbcpsorgofficeslisres

http://www.youtube.com/watch?v=gQK21572oSU

https://bcps.org/offices/lis/researchcourse/images/structural_engineering.pdf

Watch the video and then read the article looking for the answers to the folllowing three questions:

What was the problem?

What was the solution?

Why was the problem not caught before opening day?

Solution

(a) What was the problem?

Unexpected excessive lateral vibrations of the bridge. There were mainly four modes of the bridge which were excited due to  the synchronisation of lateral footfall forces with the Bridge\'s natural frequency.

--> The movements took place mainly on the south span, at a frequency of around 0.8Hz (the first south lateral mode)

--> The central span, at frequencies of just under 0.5Hz and 1.0Hz (the first and second lateral modes respectively). --> The north span at a frequency of just over 1.0Hz (the first north lateral mode).

(b) What was the solution?

The bridge was closed and analytical model was built to compare the response with the actual bridge. Pedestrain load was calculated. Lateral stiffening have been included. Also active damping control has been used.

(c) Why was the problem not caught before opening day?

The lateral loading effect on resonance has not been anticipated during the design stage.