Engineering at Nebraska, Spring 2009
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Whole Lotta Shakin Goin' On

By Carole Wilbeck
It took three months to build their model and 30 seconds for its shakedown debut, but for 10 Nebraska Engineering students at their first seismic design competition, the lessons learned stand strong.

Among 100 participating schools (dominated by programs from "the coasts"), The Durham School of Architectural Engineering and Construction team had a solid first-time experience at the Earthquake Engineering Research Institute's February 2009 conference in Salt Lake City. Coached by Terri Norton, assistant professor of construction systems engineering, the Big Red team included Durham students ranging from freshmen to seniors, including: (from architectural engineering) Sean Bergstedt, Adam Schaal, John Tran, Travis Schafer, Stephen Dodds, Isabelle Davies, Ricky Colley, Sophia Tibbo, and Iris Chan; and (from construction management) Travis Hilscher.

In preparing for this event, they met weekly (and in the final weeks, daily) in Norton's lab at The Peter Kiewit Institute, home of the college's Omaha programs. The goal was to design and build a cost-effective frame structure for a scaled high-rise from balsa wood, to perform well in an earthquake simulation.

Early on, the team made some key decisions-an important one was naming Bergstedt team leader. Bergstedt earned his bachelor's degree in physics, then decided to apply that knowledge to buildings. Now a sophomore at The Durham School, he calls himself a "transfer student" and is intent on earning his master's degree in architectural engineering. The son of a longtime woodworking hobbyist in Missouri, he brought good genes and access to tools-and discovered his leadership skills as the project progressed.

The team members got to know each other as they became familiar with the competition's challenges. They discussed the constraints, developed concepts, and shaped computer models before construction began. Their structure would have four main components: spiral exterior columns, internal reinforcements on the north/ south/east/west sides, floors-prefabricated to be symmetrical, yet each was rotated three degrees with unique internal angles-and footings.

As 2009 arrived, a small forest of balsa took shape, with thousands of cuts and one secret weapon: a potent super glue. When they saw how well it bonded the balsa joints, team members tried pouring the glue into molds for the structure's footings, which look like sugar cubes (but a whole lot stronger)!

The design's distinctive, twisting structure was patterned after a building in Dubai and selected mostly for aesthetic appeal to earn extra points with the competition's judges. The model topped out at 5' tall, and its base could not exceed 15" x 15" (to fit the competition's Quanser Shake Table II system, a bench-scale seismic simulator) for a maximum of 4,600 square inches. At a scale of 72:1, each floor of the model was two inches tall; in "real world" size the 30 floors (at 12' per floor) would make the building roughly 360' tall.

They named the model "Balsa Salsa" but hoped it wouldn't dance too much in the competition's shake test. Another secret ingredient was the addition of neo dymium magnets in clear casings, two on each side of the building, acting like shock absorbers. At ¼" diameter and 1/16" thickness, the magnets provided five pounds of pulling force, working like springs, to dampen tension and compression from the seismic simulations. The idea for the magnets came from a team member who read about them in another context and thought they'd be a good feature for this project.

The team's high-tech hopes were ultimately packaged in a low-tech combination of beverage distribution boxes, packing peanuts, and extensive shrink wrap for the wintry 15-hour drive to Salt Lake City in Bergstedt's pick-up truck. Approaching the mountains of Utah, the team finally got excited. After many all-nighters in the lab, with the last three weeks especially a blur, they rationalized the last-minute frenzy by simply saying, "We're college students."

The Nebraska team became immersed in the conference experience, which pleased Norton, who was on a student council that organized the conference's first national competition in 1995 (she also oversaw the Florida A&M team's participation in 2005, with a second place finish). When the 2009 competition scores were tallied, Nebraska's magnetic damper design helped, but the model's overall twisting design created some bigger issues with peak roof displacements and lateral/torsional loads. Overall, Nebraska placed 13th out of 18 teams in the evaluation categories: structural performance (revenue and seismic damage costs), architectural design and construction techniques. The magnets earned a second place honor for innovation, and Nebraska also gained unofficial "congeniality" points by loaning out their tools and supplies to teams in need (including a winning team), which offered some networking and understanding of other teams' approaches.

Some schools destroyed their creations on the shake table or left their models at the conference, but Nebraska transported Balsa Salsa back to Omaha, where it can inspire next year's team. Several team members are eager to try again (next year's competition is in San Francisco), and they still drop by Norton's lab sometimes to play a round of the "clothespin game" that team member Schaal developed after the glue-joint clamp phase ended (sneaking clothespins onto team members' shirttails or collars earns points).

Each team member can recount his or her contributions, and each takes away meaningful memories. Tran, who helps Norton conduct research, said the seismic design competition applies directly to what he hopes to accomplish in his career. Freshman Dodds said he most enjoyed being mentored by the whole team, which he likened to "being molded into a 'super-engineer.'" Schafer, a senior who has focused on building forensics, said he appreciated gaining a new perspective through seismic design aspects.

For Bergstedt, who is also on the research team of Moe Alahmad, assistant professor of architectural engineering, the seismic design learning experience held added dimensions with his role of organizing the work and coordinating the group—with an emphasis on decision-making, time management, problem-solving and people skills as well as technical capabilities.

Norton summarized the project's value as providing "insights about the whole design process." Having worked as a corporate recruiter, she knows how handson opportunities can really jumpstart careers and cultivate team and leadership skills. She concluded, "Learning by doing is the best way."