Is it a bridge too far?

News that tenders are invited for a project called the Floating Bridge has been met with concern by this particular Construction Week journalist. Why? Because the last time a bridge was titled with an adjective, the whole project turned into a farce. Anyone remember the Millennium Bridge? How about the Wobbly Bridge, now that must ring a few bells? After all it got worldwide coverage, albeit for the wrong reasons.

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By  Tim Wood Published  June 3, 2006

Is it a bridge too far?|~|124Tim200.jpg|~||~|News that tenders are invited for a project called the Floating Bridge has been met with concern by this particular Construction Week journalist. Why? Because the last time a bridge was titled with an adjective, the whole project turned into a farce. Anyone remember the Millennium Bridge? How about the Wobbly Bridge, now that must ring a few bells? After all it got worldwide coverage, albeit for the wrong reasons. If you don’t remember it, here is a quick reminder. The 300m, £18m (AED124 million) steel bridge in England’s capital city was expected to be an iconic structure linking the two major tourist attractions of St Paul’s Cathedral and the Tate Modern. In May 1999, piling began on the South bank with the middle sections joining in April 2000. And on opening day, June 10 2000, an estimated 100,000 people proudly crossed to the other side. But then the problems began. Although the Millennium Bridge, like all bridges, was designed to cope with a degree of movement, it soon became clear that things were going seriously awry as the deck swayed about like a drunken sailor. Elderly walkers clung helplessly to the side of the bridge. People reported feeling seasick. And after two days of random swaying, swinging and oscillating, it was closed down by embarrassed engineer, Arup. Arup decided that the problem was due to people walking the wrong way, claiming that the infamous wobble, or ‘synchronous lateral excitation’, as it put it, was due to the ‘chance correlation of footsteps when we walk in a crowd’. In other words, once it started to sway people tried to counteract it, en masse, making the problem worse. Then, after nearly two years of testing, the bridge finally reopened in February 2002 — and the swaying was banished forever. Not that I’m saying for one moment that similar problems will occur on the Creek bridge. But what happens, say, if the Floating Bridge, built out of 20m-wide hollow concrete blocks that will float on water doesn’t err… float? It is, after all, the first project of its kind in the UAE so it cannot be compared with others that may have gone boldly before it. We are told, however, that the Army has used such bridges in the past as they can be built in double quick time. Which is just as well. The winning contractor will need all of its military precision to ensure that the hopes of the 6,000 car users who will use the bridge every day once it is completed in 2007, don’t end up floating down the Creek. ||**||

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