Talk:Angers Bridge

Further information

We need more information on the failure of the Angers suspension bridge. Any volunteers, especially anyone in Angers who could supply pics or documents? Peterlewis 09:55, 6 April 2007 (UTC)

Date

On the French article the date of the collapse is given as 16 April 1850, not 15. Which is correct? Drutt (talk) 06:17, 19 May 2008 (UTC) --Depends on time zone? --AGF

Modern Marching Myth

The presentation takes for granted the 20th Century "marching in cadence" myth, and provides no reference for its having existed in Roman times. The reasons for doubting this modern myth are manifold: 1) Note that no mention is made of the Broughton Bridge collapse, which also involved soldiers purportedly marching in cadence only two decades earlier. Many sources attribute to that collapse the beginning of the supposed military prohibition, but the supposed prohibition was obviously not in force in France, if anywhere, 20 years later. 2) The fact that the construction of new suspension bridges was abandoned for the next 20 years in Europe clearly indicates that contemporary opinion placed little if any blame on the fact that the soldiers were marching in cadence. The bridge design was blamed. 3) It is not possible for a very long parade to step in unison through atmospheric audial cues. Rather their steps will be staggered according to the speed of sound in the air, damping or complicating the formation of dangerous transverse or longitudinal waves. 4) Marching over bridges is analogous to dancing on raised dance floors. When such floors give way, as occurred in Jerusalem a few year back during a wedding party, the catastrophe is not blamed on the fact that the guests were dancing, but on poor construction and the fact that the floor was loaded beyond its capacity. Nor do we hear of dancing prohibitions on bridges or balconies. Possibly the loose weight of the soldiers reacted synchronously to bridge oscillations in the manner that the weight of civilians on the Millenial Bridge supposedly did, but in the latter case the crossers were neither marching nor dancing, and it would probably have made no difference if the French soldiers had broken cadence in the unlikely case that they were in the habit of marching long distances in cadence in the first place. We simply have another example of modern mythology sanctioned by the scientific community--like the superbird myth that says the peregrine falcon can dive over 200mph, or the story that old window panes are distorted because glass is a very viscous liquid. 65.121.23.217 (talk) 15:30, 21 August 2008 (UTC)A G Foster Jr.

Can't it?? :D (I know of the window pane controversy however. The jury's still out as far as I'm concerned, as to whether it's extremely slow flowing like the tar plug at MIT(?) that's dripped 7 times since installation in the early 1900s, or just a natural reaction of the installing glazier to poor manufacturing consistency by putting the thick bit at the bottom for strength) .... For keeping in step across the bridge, who said it was audio cues? There's every chance they were keeping in time visually instead, or even by feeling vibrations through the bridge itself and stepping such as to land their feet at the most comfortable time, which may well have amplified the effect rather than weakened it. Consider 478 soldiers, each one weighing on the far side of 100kg with all their kit etc - with each thumping footstep they march, it's equivalent to bouncing a 25 ton truck off the road deck as if it were a basketball, or on the world's most powerful trick hydraulics rig. Even if there's a quarter second or so time constant (if they're, say, 6 abreast, that's more than plenty enough time at the speed of sound at sea level for the noise to go from the front row to the back; for speed of vibration through steel it's milliseconds), that's still a lot of force overall - like the truck's shock absorbers taking up the strain (heck, who's to say it was even designed to carry 50 tons at once in the first place? There's enough similar-looking modern bridges that have quite low vehicle weight restrictions on). And all it needs to do is overwhelm the weakest part of the structure with a momentary and unexpectedly amplified shock force (download "Bridge Builder" sometime and run it with the stress display turned on to see what I mean), and everything else then goes tumbling after as a rapidly reducing amount of the structure has to deal with trying to keep up both the load weight and more and more of the buckled but still heavy and attached former supports. Still so skeptical? I'd be questionable about the role of the dancers too - they're also going to be keeping in fairly strict rhythm. Lord knows the floor of my old student union nightclub used to pound quite noticably if there was a heavy set being played, and that had quite noticable over-engineering in its structure (massive steel pillars and supports etc) as it was on the first floor and designed as such a venue from scratch.... 193.63.174.10 (talk) 12:26, 21 April 2009 (UTC)

menai bridge collapses?

Without having to track down that one 20-year old book, should any library within 50 miles stock it ... have we any OTHER sources to corroborate the claims of multiple collapses of Telford's magnum opus? I've previously lived in Bangor for 3 years and looked into the history behind the area including the bridges, and not heard anything of that nature; the bridge's own wiki page states that it didn't even open until 1826, and after that the only mentions are that the (wooden) road deck needed resurfacing due to wind damage in 1839 (probably inevitable given the battering by the elements that any exposed wood with rapidly-worn-down sealing would have been exposed to in that climate), before eventual replacement with metal later in the century. No mention of any collapse, and certainly nothing for 1825 or 1836. Enough record of the fire/partial collapse of the rail portion of the Britannia Bridge however. Over to you... 193.63.174.10 (talk) 12:15, 21 April 2009 (UTC)

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