Friday, August 26, 2011
Earthquake unlikely to shake up building standards
‘It would just be too cost-prohibitive,’ official says
by margie hyslop, Staff Writer
Although engineering experts and officials across the state continue to evaluate damage from the 5.8-magnitude earthquake that gave Maryland its greatest shake in more than a century, they say few, if any, changes in building standards likely are warranted.
Most reported damage has been superficial rather than structural, state and local officials said.
State Highway Administration inspectors have checked critical components of bridges and overpasses and have found “nothing at all of concern” and no sinkholes, said Charlie Gischlar, a spokesman for the agency.
Yunfeng Zhang, associate professor at the A. James Clark School of Engineering at the University of Maryland, College Park, said modern seismic code “so far has been serving well.” The decade of the 1970s was the watershed in seismic design, he said.
Seismic codes for construction were established to save lives, not preserve buildings, Zhang said. Zhang, who specializes in seismic and structural engineering, added that in this region, most structures are built at the lowest range for seismic risk.
In the past 11 years, most local governments have adopted the International Building Code, which includes seismic considerations, to replace earlier regional standards, and some have added local amendments.
Building code requirements differ for structures based on where they are located, said Bob Frances, director of the Howard County Department of Inspections, Licenses and Permits. For example, homes in Howard County do not need to stand up to the same wind load as those in Ocean City, which is more likely to face hurricane-force winds, he said.
Just building to code makes provides a building with some resistance to earthquakes, said Ed Tudor, director of development review and permitting for Worcester County, which includes Ocean City.
“[in] a well-built, well-inspected building, you’re in pretty good shape,” he said. “Is that to say we’ll never have any earthquake damage, ever? No.”
Requiring new construction in Maryland to withstand major earthquakes does not make sense, Tudor said.
“You can’t possibly have requirements for every possible contingency,” he said. “It would just be too cost-prohibitive.”
In many cases, the bricks and stone that fell in parts of the region during Tuesday’s earthquake posed more risk to people outside than inside buildings.
Although bricks and masonry are not good at withstanding earthquakes by themselves — which makes older and historic buildings a concern — they can hold up well with steel reinforcement, Zhang said.
Around the region
In Annapolis, the State Archives building suffered some superficial masonry cracks and loose mortar, but no structural damage, said Bart L. Thomas, assistant secretary of facilities planning, design and construction for the Department of General Services.
In the State House, built in 1779, some plaster cracked in an office on the second floor, but dome repairs were not compromised and workers, secured by harnesses, stayed on the job for more than an hour-and-a-half after the shaking stopped.
Structural engineers detected no damage to government buildings in Baltimore, Thomas said.
Most buildings in Montgomery County should be able to withstand a moderate earthquake, such as this week’s, said Hadi Mansouri, a structural engineer who is acting director of permitting services for the county.
The ballroom at the Bethesda North Marriott Hotel and Conference Center, completed in 2004 as a partnership between Marriott and Montgomery County government, flooded after the quake, when caps came off sprinklers and sent water flowing, soaking the carpet.
Parts of a suspended decorative ceiling also came down in the conference center’s restaurant.
But there was no structural damage and, although a ballroom event was canceled, guests are staying in the hotel and eating in the lounge, said Tina Benjamin, director of special projects for the county’s Department of Economic Development.
But developers have told her that “they think in the next week [people] will see bits and pieces [of damage] they did not see before,” Benjamin sai
In Prince George’s County, the public schools, which opened for the year Monday, remained closed Thursday while engineers assessed structural safety at 32 buildings.
And two apartment buildings in Temple Hills were condemned and remained closed Thursday while residents waiting to return were offered shelter at the Hillcrest Heights Community Center.
Despite the temporary upheaval, environmental resources Director Samuel Wynkoop thinks Tuesday’s earthquake is unlikely to result in changes to building standards, said Prince George’s County spokesman Scott Peterson.
As a result of Tuesday’s earthquake, scientists and engineers will continue to learn and will see how the data compare to assumptions, Zhang said.
Even though California residents weather temblors like Tuesday’s regularly, the older, colder, harder bedrock in Eastern states carries the shaking farther from the quake’s epicenter, Zhang said.
That means that an earthquake on the East Coast can cause damage across a wider area than on the West Coast, where more numerous bedrock fractures also limit how far the shaking travels.
Although a lot of older buildings are not designed to withstand earthquakes, wooden buildings often are more flexible and ride out the shaking in better shape.
mhyslop@gazette.net
Staff writers C. Benjamin Ford and Andrew Ujifusa contributed to this report.
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