Faulty structural welds have been blamed for the deadly May 3 collapse of an elevated section of Mexico City’s Line 12 subway, according to a report issued Sept. 7 by Norwegian risk management firm DNV.
The five-month investigation found numerous instances of structural studs that were poorly welded, improperly located or missing entirely. The DNV report concluded the elevated steel structure and concrete rail bed were acting as “independent parallel beams,” and experiencing “loading conditions for which they were not designed.” That, in turn, led to fatigue cracks in the structure, compromising its weight-bearing capacity.