INSIGHT-Weak columns, extra floors led to Mexico school collapse, experts say

MEXICO CITY, Sept 30 (Reuters) – A Mexico City school that collapsed in a powerful earthquake last week killing 19 children buckled under the heavy weight of floors added over the years with scant steel support, according to experts and witnesses.

The tragedy at the privately owned Enrique Rebsamen school in southern Mexico City, in which seven adults also died, has become a symbol of the devastation inflicted by the country’s 7.1 magnitude quake, the worst in a generation. At least 355 people died in the capital and surrounding states.

“The building was badly designed, poorly calculated and poorly constructed,” said Alfredo Perez, a 52-year old civil engineer who dashed to the school shortly after the Sept. 19 quake to help rescue efforts. “The reinforced concrete doesn’t comply with specifications in construction regulations.”

Alongside rescue workers, Perez said, he pulled bodies from the rubble. Then he sat in one of the undamaged classrooms and drew plans detailing potential design failures in the collapsed building.

Reuters showed those plans to six structural engineers along with Reuters’ photos of the ruined structure. They independently concluded that the structure’s columns lacked sufficient steel rebar to support all four floors and prevent them from snapping in such a powerful earthquake.

While the quantity of steel required under Mexico’s stringent post-1985 building code varies depending on the size of structure, all six engineers said the building’s columns were built with too little steel to withstand strong quakes.

Perez and another engineer specified that columns appeared to have less than half the required amount of steel reinforcement. They base their view on the number of vertical and horizontal steel rebar rods in the columns, which are visible in Reuters photos along with the measurements in Perez’s plans.

“It comes down to the lack of steel,” said Troy Morgan, a New York-based senior managing engineer at…

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