Passenger Trains > Mexico City rail bridge collapse

Just on KTTV 11 TV in Los Angeles showed a bridge collapse onto a street in Mexico City Mexico. TV said passenger probably transit.

https://www.theguardian.com/world/2021/may/04/mexico-city-overpass-collapse-metro-train-carriages

"A rescue operation was under way after a Mexico City metro overpass partially collapsed on Monday night. At least 13 people died in the incident and about 70 were injured, civil protection authorities in Mexico said."

"Videos on Mexican television and social media showed train cars hanging in mid-air as sirens blared nearby. Footage on Milenio TV showed the overpass collapsing on to cars on a road below."

"Mexico City’s mayor, Claudia Sheinbaum, said on Twitter that a support beam had given way, causing the overpass to collapse.  Sheinbaum said at least one car was trapped under the rubble and emergency workers were searching for survivors. The accident happened at around 10:30pm local time on the metro’s Line 12."

While showing a visual that said "Mexico City bridge collapse" on tonight's ABC-7 News from San Francisco, the anchor distinctly stated that "...a subway bridge collapsed in New York City."

I wish I could say this was surprising, the elevated section of Linea 12 in Tlahuac has had multiple issues since it opened in 2012. In 2014 the elevated section had to be closed for over a year. With only two years of service, the geometry of the track was so out of alignment, several kilometers of rail and ties had to be replaced, along with renewed ballast. Wheelsets on many of the trains were so warn, they had to be removed from service. In the 2017 earthquake, several spans nearly collapsed after several of the piers failed, and several seismic retainers snapped loose...

After a cursory look at the span that collapsed tonight I saw some interesting things. This span has a two tracks and a switch on it (for a siding). Despite this there are only two girders for the span, along with a smaller skewed girder that meets the main girder under the switch.  The adjacent span has three full girders for comparison.  In addition this span also carries quite a bit of catenary gear.  Looking at the accident photos, the girder appears to have failed right underneath the switch, where the smaller girder meets the main girder. Was the load factor insufficient for this span? Dunno, but this failure, and the other issues this viaduct has had in it's short life, you have to wonder...

I would love to know which engineering firm designed the viaduct. The track materials were sourced from several European countries (France, Spain, UK)...

Edit: My above question was answered in the following article (in Spanish, but easily translatable). The engineering was done by Alstom and a company owned by Carlos Slim. The article also details the issues the line has had...
https://expansion.mx/negocios/2014/03/11/quien-construyo-la-linea-12-del-metro

Edit: This survelliance video also shows the span failing in the area directly below the switch...
https://twitter.com/OnceNoticiasTV/status/1389431367264575488?s=20

Photo showing possible failure point. Photos from Google...



Edited 5 time(s). Last edit at 05/04/21 04:12 by ats90mph.

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Thanks, very detailed report.

Bob

We have steel els in Brooklyn built in 1884 for a splinter fleet with steam locos, now carrying heavy steel subway trains. They don't collapse into the street.

What they built in Mexico City looks like a cheap highway span. Can North America do anything right anymore ? 

Here come the arm chair experts...

joemvcnj Wrote:
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Can North America do anything right
> anymore ? 

Since you asked, no. 

Lotsa pix:    https://www.eng-tips.com/viewthread.cfm?qid=482767

Thanks for the link.  Great site for engineering info.

That link is super informative. A great fact-centered discussion. 

RRBaron Wrote:
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> joemvcnj Wrote:
> --------------------------------------------------
> -----
> Can North America do anything right
> > anymore ? 
>
> Since you asked, no. 

Wait...what?

New rail structures have been built all over the place in North America without any problems.  This includes fairly recent elevated urban rail systems (Chicago Orange Line) and new bridges (Norfolk Southern Genesee Arch Bridge in New York).

Failures of transportation structures have happened in the past in North America.  The Quebec Bridge failed twice (1907 & 1916) during construction with a total of 88 casualties.  The Tacoma Narrows Bridge collapsed due to wind in 1940.   The Silver Bridge collapsed in 1967 killing 46 people.

Disastrous failures of transportation structures have happened before.  Fortunately, they are rare events.



Edited 1 time(s). Last edit at 05/05/21 20:51 by RuleG.

That part that collapsed belongs to a subway line in Mexico City, which even since it was being built already had problems, because it was built badly, in fact no matter how many times they remodel it, it will never look good (the one that in At that time he was the head of government, which is equivalent to the mayor in Mexico City, in order to keep most of the money, he built it as if it were the monorail that appears in The Simpsons) and in fact shortly before this tragedy, almost a train was derailed on that line.