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.
DNV’s report added that deficiencies in the beams and framework design may also have contributed to the collapse, which occurred as a four-car subway neared a suburban station, sending two rail cars plummeting approximately 16 ft into the median of an underlying boulevard, killing 26 people.
结果证实了DNV的初步发现，该发现是在6月中旬发布的。最初计划于8月23日发布，最新报告应该公司的要求推迟了两周，以便另一批国际专家可以对DNV所谓的“崩溃分析中最复杂的阶段”进行“内部审查”。
In addition to the DNV investigation, the collapse is also under study by Mexico City’s attorney general and the College of Civil Engineers of Mexico, the country’s civil engineering professional society.
自2012年开始运营以来，该12.6英里以13亿美元的价格建造了争议，并指控成本超支，设计缺陷和政府腐败。2014 - 15年度进行了18个月的部分关闭，进行了赛道和结构修理，这引发了一项调查，揭示了许多有缺陷的建筑材料和可疑项目监督的情况，导致刑事起诉数名高级项目官员。
Mexico’s president Andrés Manuel López Obrador has stated that Line 12’s elevated sections will reopen by early 2022, with all reconstruction work to be paid for by billionaire Carlos Slim, owner of Carso Infraestructura y Construcción (CICSA), which was part of the subway line’s original construction consortium.
上个月，墨西哥城的建议技术委员会建议重建包括重新定位和重新调整高架部分，并确保符合美国焊接协会标准的焊接检查和梁修复。该小组还建议使用碳纤维夹克安装混凝土支撑柱，以提高结构容量。
Just hours after DNV’s latest report was released, Mexico City was shaken by a magnitude 7.1 earthquake centered approximately 230 miles away near Acapulco. Following a brief shutdown of the city’s subway system all lines were back in operation the following morning.
