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Author Topic: "20 dead" in metro overpass collapse, Mexico City.  (Read 675 times)
broadgage
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« on: May 04, 2021, 08:42:34 am »

News reports state.
https://www.bbc.co.uk/news/world-latin-america-56977129

Pictures from the scene show collapse of Metro overpass whilst a train was on it, many lives lost both on the train and crushed under the fallen structure.
Early reports suggest that structural failure was the cause, rather than the collapse being the result of a railway accident.

WARNING the above link contains contains images from the scene which some might consider inappropriate, but as these are already in the public domain I saw no harm in quoting.
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A proper intercity train has a minimum of 8 coaches, gangwayed throughout, with first at one end, and a full sized buffet car between first and standard.
It has space for cycles, surfboards,luggage etc.
A 5 car DMU (Diesel Multiple Unit) is not a proper inter-city train. The 5+5 and 9 car DMUs are almost as bad.
broadgage
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« Reply #1 on: May 04, 2021, 08:56:34 am »

Slightly later reports suggest that the structure may have been damaged in an earthquake a few years ago, cracks had been reported.
No reports of any earthquake at the time of the accident.

Most of the dead and injured have been removed from the remains of the train, but is feared that there may be more casualties  under the collapsed structure, either pedestrians or occupants of vehicles.

One video from the scene shows a survivor being carried down a ladder by firefighters, and others being treated at the scene for various injuries.

At least one (not very clear) video on youtube shows the actual collapse, most others show show the immediate aftermath and the rescue efforts.

« Last Edit: May 04, 2021, 09:05:58 am by broadgage » Logged

A proper intercity train has a minimum of 8 coaches, gangwayed throughout, with first at one end, and a full sized buffet car between first and standard.
It has space for cycles, surfboards,luggage etc.
A 5 car DMU (Diesel Multiple Unit) is not a proper inter-city train. The 5+5 and 9 car DMUs are almost as bad.
stuving
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« Reply #2 on: June 17, 2021, 09:14:01 am »

There is an initial report on this from DNV*. The report itself is of course in Spanish (though I suspect it was written in English and translated!), but has loads of pictures and some sense can be made of those using the NYT report. The BBC» (British Broadcasting Corporation - home page) has a report, but that link comes courtesy of the NY Times, which has a more detailed report. Basically, it was shoddy construction:
Quote
MEXICO CITY — Construction errors led to the May collapse of an overpass in Mexico City’s subway system that killed 26 people and injured scores more, according to the preliminary results of an independent investigation released by the city’s government on Wednesday.

The report, produced by the Norwegian risk management company DNV, suggests that serious problems with the welding and placement of metal studs, linchpins of the entire structure, directly contributed to the collapse.

“We can preliminarily state that the incident was caused by a structural failure,” the report said, citing “deficiencies in the construction process.”

The results support the findings of a New York Times investigation that highlighted shoddy construction on the metro line. Some of the studs holding the structure together appeared to have failed because of bad welds, The Times found, a crucial mistake that probably caused the overpass to give way.

A Times investigation shows the serious construction flaws and political pressure behind a tragedy that threatens two of Mexico’s most prominent figures.

Engineers consulted by The Times pointed to the presence of ceramic rings, or ferrules, left in place after the welding process, and to irregularly placed studs as evidence of subpar workmanship — findings that were confirmed by the DNV investigation.

Its report documented a “failure to remove the protective ceramic” around the studs, which “reduced the area of adhesion” with the concrete that held up the tracks. Too few studs were used to fuse the structure together, and their placement was inconsistent, something that “contradicts the design” of the overpass, the report said, echoing another finding of the Times investigation.


* DNV are the "Norwegian Lloyds", and originally a ship classification society and shipping registrar. Having broadened their techinical field of operations (to railway infrastructure, but not only that) there don't seem to be any good labels for their current business. So the BBC call them "auditor", the NY Times says "risk management company" - maybe "Like Veritas" is as good as anything!
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