# So a one-metre piece of concrete falling off of an overpass is just routine? **URL:** \ **Category:** Factual Questions\ **Created:** [October 1, 2006, 3:06pm UTC](https://boards.straightdope.com/t/so-a-one-metre-piece-of-concrete-falling-off-of-an-overpass-is-just-routine/374833 "2006-10-01T15:06:31Z")\ **Posts on this page:** 14\ **Page:** 1
**Author:** ![Rysto](https://avatars.discourse-cdn.com/v4/letter/r/ecccb3/32.png) [@Rysto](https://boards.straightdope.com/u/Rysto)\ **Post date:** [October 1, 2006, 3:06pm UTC](https://boards.straightdope.com/t/so-a-one-metre-piece-of-concrete-falling-off-of-an-overpass-is-just-routine/374833/1 "2006-10-01T15:06:31Z")
Yesterday, an overpass in Quebec collapsed. More than an hour before it happened, a man called the police to report that a [one metre block of concrete](http://www.thestar.com/NASApp/cs/ContentServer?pagename=thestar/Layout/Article_Type1&c=Article&cid=1159654214829&call_pageid=968332188492&col=968793972154&t=TS_Home) had fallen from the overpass onto the highway below. A [spokesman](http://www.cbc.ca/canada/story/2006/10/01/overpass-collapse.html) for Transport Quebec said: > [@](#): > > Portions of structures like this fall off all the time and most of the time that does not affect the stability of the bridge, Is there any truth to this statement? Small pieces of concrete I could see, maybe, but if the debris was large enough to require a maintenance crew to clean it up, surely there had to be significant pieces of concrete coming off of the bridge? Any structural engineers want to chime in? ---
**Author:** ![Rick](https://avatars.discourse-cdn.com/v4/letter/r/9f8e36/32.png) [@Rick](https://boards.straightdope.com/u/Rick)\ **Post date:** [October 1, 2006, 3:33pm UTC](https://boards.straightdope.com/t/so-a-one-metre-piece-of-concrete-falling-off-of-an-overpass-is-just-routine/374833/2 "2006-10-01T15:33:30Z")
Notice the spokesmand did say what size piece is normal to have fall off. :dubious: A 1 meter chunk? :eek: Close the damn road and investigate. Now. The only think I can think of that would prevent such a more right now is that they did not understand or believe the caller. Even so they dispatched a crew before the colapse. The crew should have shut it down ASAP. ---
**Author:** ![jasonh300](https://avatars.discourse-cdn.com/v4/letter/j/46a35a/32.png) [@jasonh300](https://boards.straightdope.com/u/jasonh300)\ **Post date:** [October 1, 2006, 5:45pm UTC](https://boards.straightdope.com/t/so-a-one-metre-piece-of-concrete-falling-off-of-an-overpass-is-just-routine/374833/3 "2006-10-01T17:45:11Z")
Where did this one meter chunk fall?? Are they talking a cubic meter? That would weigh about a ton! I assume it didn’t fall onto the lower roadway. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [October 1, 2006, 6:48pm UTC](https://boards.straightdope.com/t/so-a-one-metre-piece-of-concrete-falling-off-of-an-overpass-is-just-routine/374833/4 "2006-10-01T18:48:07Z")
> [@](#): > > Are they talking a cubic meter? That would weigh about a ton! More like 4 or 5 tons. A cubic meter of water is a ton, but most minerals are about 5 times the density of water. ---
**Author:** ![Gorsnak](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gorsnak/32/7587_2.png) [@Gorsnak](https://boards.straightdope.com/u/Gorsnak)\ **Post date:** [October 1, 2006, 8:16pm UTC](https://boards.straightdope.com/t/so-a-one-metre-piece-of-concrete-falling-off-of-an-overpass-is-just-routine/374833/5 "2006-10-01T20:16:26Z")
Apparently the piece that fell off earlier wasn’t that large: > [@Globe and Mail](#): > > Mr. Despres said an inspector called to the scene Saturday found no reason to close the overpass after conducting a visual and auditory review. The department official was called after a piece of concrete measuring 38 centimetres by 18 centimetres fell off the overpass. > > The structure collapsed four minutes after a second chunk of concrete fell off less than an hour after the first. [link](http://www.theglobeandmail.com/servlet/story/RTGAM.20061001.wmoverpass1001/BNStory/National/home) I have no idea if there was incompetence on the part of the inspector or not, just passing along a few details. ---
**Author:** ![spingears](https://avatars.discourse-cdn.com/v4/letter/s/ebca7d/32.png) [@spingears](https://boards.straightdope.com/u/spingears)\ **Post date:** [October 1, 2006, 8:37pm UTC](https://boards.straightdope.com/t/so-a-one-metre-piece-of-concrete-falling-off-of-an-overpass-is-just-routine/374833/6 "2006-10-01T20:37:17Z")
[QUOTE=Rysto] Yesterday, an overpass in Quebec collapsed. More than an hour before it happened, a man called the police to report that a [one metre block of concrete](http://www.thestar.com/NASApp/cs/ContentServer?pagename=thestar/Layout/Article_Type1&c=Article&cid=1159654214829&call_pageid=968332188492&col=968793972154&t=TS_Home) had fallen from the overpass onto the highway below. A [spokesman](http://www.cbc.ca/canada/story/2006/10/01/overpass-collapse.html) for Transport Quebec said: [/QUOTE] Nevermind the bridge (overpass) Post the lower highway as to danger or better yet set up a detour. :rolleyes: ---
**Author:** ![Joey\_P](https://avatars.discourse-cdn.com/v4/letter/j/919ad9/32.png) [@Joey\_P](https://boards.straightdope.com/u/Joey_P)\ **Post date:** [October 2, 2006, 4:30am UTC](https://boards.straightdope.com/t/so-a-one-metre-piece-of-concrete-falling-off-of-an-overpass-is-just-routine/374833/7 "2006-10-02T04:30:49Z")
[QUOTE=spingears] Nevermind the bridge (overpass) Post the lower highway as to danger or better yet set up a detour. :rolleyes: [/QUOTE] DETOUR AHEAD… TAKE NEXT EXIT, GO OVER BRIDGE… Or WARNING, FAILING BRIDGE, PLEASE GO OVER, NOT UNDER. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [October 2, 2006, 8:52am UTC](https://boards.straightdope.com/t/so-a-one-metre-piece-of-concrete-falling-off-of-an-overpass-is-just-routine/374833/8 "2006-10-02T08:52:15Z")
Or perhaps: DO NOT DRIVE UNDER BRIDGE IF IT FALLS ON YOU ---
**Author:** ![Joey\_P](https://avatars.discourse-cdn.com/v4/letter/j/919ad9/32.png) [@Joey\_P](https://boards.straightdope.com/u/Joey_P)\ **Post date:** [October 2, 2006, 11:13am UTC](https://boards.straightdope.com/t/so-a-one-metre-piece-of-concrete-falling-off-of-an-overpass-is-just-routine/374833/9 "2006-10-02T11:13:20Z")
Do Not Drive Over Bridge After It Collapses ---
**Author:** ![BobLibDem](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/boblibdem/32/3149_2.png) [@BobLibDem](https://boards.straightdope.com/u/BobLibDem)\ **Post date:** [October 2, 2006, 12:03pm UTC](https://boards.straightdope.com/t/so-a-one-metre-piece-of-concrete-falling-off-of-an-overpass-is-just-routine/374833/10 "2006-10-02T12:03:23Z")
The answer to the question as posed is: it depends. I haven’t seen photos or diagrams yet to really know what happened or even what type of bridge it was. Concrete can and does fall from the underside of bridge decks with no significance other than to the poor guy below whose car gets the brunt of a fall of a piece of it. From the descriptions, it rather sounds like the chunks came off the underside of a girder. Again, depending on what caused the spalling and where it was, it could either be insignificant or catastrophic. Again I don’t know what kind of bridge it was. If I had to bet, it would be that this was a bridge with prestressed beams and the concrete was not properly compacted or vibrated in the forms. This allowed brine to eventually find its way to the bottom of the beam and start working on the prestressing strands. The rusting strands expand and blow away the concrete under them. At some section of the beam, the rusting strands snap one by one, and the resulting deflections blow off the chunks noted. At some point, the beam has lost enough strands that the remaining strands cannot pick up the slack and the beam fails suddenly. Did the inspector miss something? To be honest, I doubt it. It’s possible that all this was going on inside a beam that from the outside looked normal up until just before the incident. And if the inspection was not of the arms length up close variety, then it could very easily have been missed. These are my best guesses based on 28 years of design/load rating/management of bridges. The guys in Quebec with the plans and the photos are going to have the authoritative answers when they complete their investigation. ---
**Author:** ![Cervaise](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cervaise/32/16693_2.png) [@Cervaise](https://boards.straightdope.com/u/Cervaise)\ **Post date:** [October 2, 2006, 2:09pm UTC](https://boards.straightdope.com/t/so-a-one-metre-piece-of-concrete-falling-off-of-an-overpass-is-just-routine/374833/11 "2006-10-02T14:09:53Z")
[QUOTE=BobLibDem] I haven’t seen photos or diagrams yet to really know what happened or even what type of bridge it was. [/QUOTE] [pictures](http://www.thestar.com/NASApp/cs/ContentServer?pagename=thestar/Render&c=Gallery&cid=1159740611941) ---
**Author:** ![Hypnagogic\_Jerk](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hypnagogic_jerk/32/4252_2.png) [@Hypnagogic\_Jerk](https://boards.straightdope.com/u/Hypnagogic_Jerk)\ **Post date:** [October 4, 2006, 4:13am UTC](https://boards.straightdope.com/t/so-a-one-metre-piece-of-concrete-falling-off-of-an-overpass-is-just-routine/374833/12 "2006-10-04T04:13:49Z")
It wasn’t actually an inspector who first came to check the structure, but a patrolman from the ministry of Transportation, who doesn’t have any special knowledge about bridges and other structures. He also didn’t have any power to order road closures. He picked up the debris and called his supervisors to recommend that the overpass be inspected soon by an engineer. Some time later, there was a second call to police to report falling debris. Apparently the patrolman was sent on the scene again – and a structural engineer as well – but the structure collapsed before they got there. This is what I’ve pieced together from articles in _La Presse_ and _Le Devoir_. We’ll have more information after the commission submits its report. ---
**Author:** ![sturmhauke](https://avatars.discourse-cdn.com/v4/letter/s/e47c2d/32.png) [@sturmhauke](https://boards.straightdope.com/u/sturmhauke)\ **Post date:** [October 4, 2006, 8:09am UTC](https://boards.straightdope.com/t/so-a-one-metre-piece-of-concrete-falling-off-of-an-overpass-is-just-routine/374833/13 "2006-10-04T08:09:04Z")
Out here in the Earthquake State, Caltrans jumps all over any sign of structural damage whatsoever. It’s a pain in the ass when they take a decade to reopen a freeway, but at least there’s some assurance it won’t fall on your head. ---
**Author:** ![Quartz](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/quartz/32/267_2.png) [@Quartz](https://boards.straightdope.com/u/Quartz)\ **Post date:** [October 4, 2006, 9:20am UTC](https://boards.straightdope.com/t/so-a-one-metre-piece-of-concrete-falling-off-of-an-overpass-is-just-routine/374833/14 "2006-10-04T09:20:20Z")
[QUOTE=Chronos] A cubic meter of water is a ton, [/QUOTE] \A cubic metre of water is a _tonne_. Metric measurements, you know… \