Quake codes studied after school collapse
MEXICO CITY — On paper at least, the Mexico City school appeared to be structurally sound and built to withstand a major earthquake.
But it collapsed, killing 26 people, most of them children. And authorities are looking into whether an apartment reportedly built on top of the two-story school was to blame.
Claudia Sheinbaum, the borough president of the southern Mexico City district where the school went down in the 7.1 magnitude quake, told a news conference Tuesday that the school appeared to have its paperwork in order, at least according to documents filed by architects and engineers who supposedly inspected the structure. She said an investigation was being launched to look for any abnormalities not revealed in those documents.
“We can’t stop just with the paperwork,” Sheinbaum said. “We are going to do a review of the building itself.”
Burden on owner
Authorities said the owner of the privately owned Enrique Rebsamen school built an apartment for herself on top of the collapsed wing, which local media said included a Jacuzzi, and were looking into whether the extra weight might have played a role in the collapse.
Sheinbaum said she didn’t know if that was true, but said the owner, Mónica García Villegas, had a permit dating back to 1983 to build a school and apartments on the lot, though it was unclear whether she had permission to add a third story to the section of the school that collapsed.
The school was just one of dozens of buildings that collapsed in the Sept. 19 quake that killed at least 333 people, 194 of them in Mexico City. Questions have been raised about whether new building standards put in place after a 1985 quake that killed 9,500 people had been adequately followed.
Although construction began on the school in 1983 — two years before the new codes went into effect — it was expanded over the next 34 years with no evidence of noncompliance, Sheinbaum said. She said the only immediately evident paperwork problems during that time were two cases of unregistered expansion work, and Garcia Villegas paid a fine for not registering the work and was allowed to proceed.
On Tuesday, Meyer Klip Gervita, head of the Institute of Administrative Verification, said that earlier this year authorities had asked the school to stop operating because no record of its zoning permit could be found. But the school appealed and remained open while the case made its way through court. The apparent violation was not enough to force the school’s closure. The institute was created to ensure compliance with city building ordinances among other responsibilities. Phone calls to a number registered to Garcia Villegas, who was pulled alive from the rubble, rang unanswered.
Seismologists and engineers say the Mexico City buildings most at risk in a quake are those, like the school building, that were built atop an Aztec-era lake bed, where the muddy soil can amplify earthquake waves.
Shoddy engineering
But, although an architect signed a document certifying the school was structurally sound, experts questioned the method used to evaluate it, which Sheinbaum said involved piling sandbags on its upper floors to simulate 85 percent of the structure’s maximum designcarrying weight, and then measuring the resulting floor sag.
Kit Miyamoto, a structural engineer and California Seismic Safety Commissioner, said sandbags can’t test for earthquake resistance.
“Seismic is a lateral force, so if you just put a whole bunch of sandbags it is not going to tell you the story of the seismic capacity of the building at all,” Miyamoto said. “You can do testing, to determine what kind of reinforcement” a building has, including ground-penetrating radar or exposing rebar.
The school’s first wing was built in 1983, but other additions and floors were added over the years, said Francisco Garcia Alvarez, president of the Mexican Society of Structural Engineers, who evaluated the school site after its collapse.
A third floor appeared to have been added recently to the original 1983 structure that was toppled in the quake, raising questions about what construction permits, if any, the school had obtained, how recently it had been inspected and what architectural plans were submitted in the first place.
Paperwork filed as recently as June by a private architect working for the school asserted that the parcel had not been modified in a way that would violate the permitted land use.
The quake, whose epicenter was only about 100 miles from the capital, hit the city’s south side where the school is located with a force much stronger than the original school structure was built to withstand in the early 1980s, Garcia Alvarez said.
That caused a failure in the building’s joints where the columns met the beams, he said, noting that the addition of a third floor would have added weight to the structure. Still, he said, its possible role in the collapse needed further study.
Sheinbaum, who is widely expected to run for mayor, faces heightened political scrutiny over the school’s collapse, which killed 19 children and seven adults, leaving behind a pile of wreckage visible in a cordoned-off street of the leafy neighborhood manned by soldiers.