91视频

Construction that can generate seismic issues

Unreinforced masonry: load-bearing walls, parapets or other elements made of brick, cinder block or other masonry materials not braced with reinforcing beams.

Pre-cast concrete: walls made of concrete cast in molds or forms off-site and then transported to the project site. Important structural features may have poor connections.

Tilt-up construction: buildings built from concrete slabs poured on the building floor and then lifted into place with a crane. Heavy concrete walls may be braced insufficiently.

Wood: light structures often with poor connections between walls and foundations. If not secured, these buildings can fall off their foundations.

In Oregon, more than 307,000 students attend public school in buildings that experts say would be at risk of collapse if a big earthquake were to hit the Pacific Northwest. But school and government officials and safety advocates are struggling to find a solution to pay for seismic upgrades.

There are two root causes of Oregon’s unpreparedness. First, until 1995, building codes did not account for seismic resistance, and buildings were not designed with connections and strength necessary to withstand the lateral loads that would occur during a large earthquake.

Second, seismically deficient structures have survived decades in Oregon because of infrequent earthquakes.

鈥淛apan is so much more advanced than we are, in terms of seismic safety,鈥� said Yumei Wang, a geotechnical engineer and team leader for geo-hazards in the Oregon Department of Geology and Mineral Industries. 鈥淚t’s shocking.鈥�

The largest earthquake danger in Oregon comes from the Cascadia fault, which is close to the coastline.

鈥淚n geologic terms, the (fault) goes off like clockwork,鈥� Wang said.

Though many experts cite data suggesting there is a 10 to 15 percent chance that a major Cascadia earthquake will occur in the next 50 years, Oregon State University professor Chris Goldfinger, a nationally recognized expert, says the likelihood is probably greater. He frequently presents a 鈥渇ailure analysis鈥� that states there is an 80 percent chance of a rupture of the southern part of the Cascadia fault in the next 50 years.

That 鈥渂ig one鈥� could have a magnitude as large as 9.2 and cause shaking for more than three minutes. In that circumstance, approximately 649 of Oregon’s public K-12 schools would be prone or likely to collapse, according to a DOGAMI survey spearheaded by Wang. Schools in session would hold more than 307,000 students.

Eighty-six of those schools 鈥� with approximately 34,000 students 鈥� feature unreinforced masonry. Such construction was deemed illegal for California schools after more than 100 collapsed in the 1933 Long Beach earthquake.

Portland Public Schools representatives, however, stand by a 2009 study it commissioned that holds a less extreme view of the dangers. But even that study notes significant concerns for many PPS buildings.

The Fernwood building for Beverly Cleary school, for instance, has unreinforced masonry. Money from a 1995 bond paid for a partial seismic upgrade, which braced stairways and tied back the building’s parapet so it wouldn’t crumble off and block the entrance. But such work was not enough to ensure safety of occupants, according to the PPS study.

鈥淭he previous approach of 鈥榗ollapse prevention and safe exiting,’ in our opinion, is not sufficient to protect the life safety of building occupants during a 鈥� earthquake,鈥� KPFF wrote in the report’s recommendations.

The KPFF study evaluated 12 representative PPS schools and extrapolated the data for the district’s 95 schools. According to the study, seismic safety upgrades totaling $422 million are needed to bring all but two of the district’s school buildings up to life-safety levels. Life safety means that people can safely exit the building.

The $548 million construction bond measure that failed in May called for more work than only seismic upgrades. Nine schools would have been brought up to seismic standards and five others would have received structural improvements. The district’s strategy is to upgrade a school all at once, rather than perform seismic work and return to take on other projects later.

鈥淭he amount of work you need to do to fully retrofit a building requires taking walls apart. When you take the walls apart, it makes sense to do everything at once,鈥� PPS spokesman Matt Shelby said.

Other funding possibilities exist for school seismic upgrades. For instance, schools will be able to apply for money from a state Seismic Rehabilitation Grant program, which was expected to receive $7.5 million for next year through state Senate Bill 5508.

The new 鈥淐ool Schools鈥� program also could provide money for seismic upgrades, according to Christine Miles, a spokeswoman for Gov. John Kitzhaber. Seismic upgrades would have to be partnered with energy-efficiency upgrades, however, to be eligible.

PPS is holding listening sessions to assemble plans for its next bond request, which could come in fall 2012, according to PPS Chief Operating Officer C.J. Sylvester.

Engineers, architects and researchers at an American Institute of Architects-Portland event last week spoke up for seismic upgrades in schools.

AIA President Kurt Haapala responded to a concern that voters considered construction industry support of the PPS bond as self-serving.

鈥淲e are parents of children too. I don’t care what profession you are 鈥� you think about your children and your children’s safety,鈥� Haapala said. 鈥淏ut this makes me want to be thoughtful about how we work with PPS and others.鈥�

Wang hopes action will be taken.

鈥淲e should make it a top priority that our collapse-prone school buildings don’t collapse,鈥� she said. 鈥淭here is a mandate to send kids to school. They are a vulnerable population, and this is something that we as a society need to address better.鈥�