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Researchers test durability of building materials in major earthquakes

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Researchers tested building materials to see how they perform during major earthquakes Monday at the University of California, San Diego’s Englekirk Structural Engineering Research Center.

Results of the test will help generate revisions to the building code and ensure homes are safer and sturdier in earthquake prone regions, said Richard Klinger, a civil engineering professor at the University of Texas at Austin.

Klinger was among the professors and graduate students hailing from universities nationwide, collaborating to design and execute the test. The $950,000 project was funded by the National Science Foundation and the National Concrete Masonry Association.

During the test, a single-story home similar in construction to many homes in San Diego, rattled atop a “shake table” as a simulated magnitude 6.6 earthquake struck. Moments after the shaking began, the brick veneer of one of the four walls crumbled, revealing the wood-stud frame and gypsum wallboard.

Different ties were used to link brick masonry to the wooden frame on two opposing walls. Both sides were designed to meet current building codes, which require homes be designed to withstand a 6.6 quake, Klinger said.

The ties used on the left side were slightly thinner and more flexible than the ties used on the right side of the building, said Terry Curtis, chief executive officer of Heckman Building Products Inc., a manufacturer of masonry anchors and ties. However the ties used on the left side are more commonly used in home construction in seismically active California.

Klinger was surprised the wall did not withstand the quake. Based on the sophisticated models and calculations generated by researchers, the wall was expected to stand strong through the 6.6 magnitude test and topple during a later 6.8 magnitude test.

Each time magnitude increases by 0.1, the intensity of an earthquake increases 10 times. The devastating Northridge earthquake in 1994 registered a 6.7 magnitude.

Researchers later tested the structure’s strength with a quake more intense than Northridge. A 6.8 magnitude earthquake has a 2 percent likelihood of striking in the region within 50 years. An earthquake of that intensity typically occurs once in 2,500 years, said Seong Woo Jo, a student working toward his doctorate degree at University of Texas at Austin.

When hit by the simulated 6.8 quake, the remaining masonry on the partially collapsed wall also crumbled, landing in a pile of mortar and bricks.

The test of the standard construction home was the first of its kind in the world, and is likely to help develop better homebuilding methods, said Mark McGinley, a professor of civil and environmental engineering at the University of Louisville.

“We want to learn how we can change how we build it, to make walls perform even better,” McGinley said.

Video: UCSD's earthquake simulation


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