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Friday, April 30, 2010

Tsunami Study Eyes Isle Building Safety

Honolulu Star Bulletin
Most medium-to-tall reinforced concrete structures would likely stand, a professor says

A University of Hawaii engineering professor says most medium-to-tall reinforced concrete buildings in Hawaii would likely survive a tsunami.

But Ian Robertson is worried about the foundations of shorter structures and wooden buildings, including some in Waikiki.

Once guidelines in a construction structural study are completed this summer, Robertson said he will recommend assessing the ability of the buildings in Hawaii to withstand a tsunami.

The $1.3 million study, funded by the National Science Foundation, was prompted by the destruction that occurred in the tsunami in the Indian Ocean in 2004.

Robertson and engineers from the University of Oregon and University of Michigan have developed ways to improve the resistance of buildings to a tsunami.

He said the study will suggest design guidelines that could be adopted by Honolulu for major Hawaii concrete contractors working in tsunami inundation areas.

Civil Defense Vice Director Edward Teixeira said he is in favor of conducting an tsunami assessment of buildings but is wary of the cost.

Kaleo Keolanui, president of the Hawaii Hotel and Visitor Industry Security Association, said he is willing to explore the idea of doing an assessment but noted that the economy is down and an assessment would add to costs.

"Obviously, the cost would have to be passed onto somebody," he said.

Teixeira said as shown in the tsunami of 2004 in the Indian Ocean, people in reinforced steel structures survived the wave inundation.

Teixeira said there has been no tsunami assessment of survivability of buildings in Hawaii.

Teixeira said he agreed with Robertson that people in wooden buildings near the shoreline should evacuate their structures.

Teixeira said Civil Defense recommends people vertically evacuate to at least the third floor of reinforced steel concrete buildings that are six stories or higher.

He said counties vary in their recommendations to.

For instance, Hawaii County emphasizes evacuation from the tsunami zone, except for warning with short notices, whereas Maui County recommends vertical evacuation in Kaanapali.

Robertson said the new guidelines are based on what engineers have learned about the survivability of buildings in tsunamis in the Indian Ocean in 2004 and in Chile in late February.

"In the Chile tsunami, there were a large number of reinforced concrete buildings that survived intact," Robertson said. "I think based on what we've observed in previous tsunamis, we're confident the buildings (in Waikiki) will perform well."

Robertson said a study looking at medium-height buildings indicates the design guidelines would add just 1 to 8 percent to the structural cost or about 2 percent to the overall construction cost. "It's definitely feasible," he said.

Robertson said engineers will recommend the concrete construction of "breakaway walls" at the ground level of high-rise structures.

If a tsunami wave struck, the building's foundations would have a better chance of surviving if walls at the ground level broke away from the reinforced steel foundation, rather than place more stress on the structure.

He said during a tsunami, shipping containers could become floating rams that could cause much damage.

He said buildings more likely to survive a tsunami have deep piles or drilled shafts in the ground.