UW News

December 23, 1996

Engineers celebrate a topping out with a shake, rattle and roll

It was shakes and congratulations all round this week when the University of Washington Structures Laboratory celebrated the topping out of a four-year building project. More accurately, a table- topping out.

With an ear-splitting roar, the lab’s new shaking table, a massive device for the testing of structures and materials for earthquake studies, made its inaugural shake. The 15,000-pound steel table has been designed and built by four present and former graduate students at the UW, under the tutelage of Prof. John Stanton, the director of the laboratory, which is part of the Department of Civil Engineering.

The 8-feet by 16-feet shaking table, one of only a handful of testing tables of this size in the U.S., will be used to study seismic effects on soils, and on structures such as buildings and bridges. Its massive oil-pumped jacks can push the table back and forth with up to 55 tons of force, simulating what the table’s designer, Jeffrey Curtis, describes as “a very, very severe earthquake.”

Besides Curtis, of Arlington, WA, who has a master’s degree in structural engineering from the UW, the table-top team consists of graduate students Jim McElroy of Cleveland and Mark Bergin of Juneau, Alaska, and Phillip Donovan from Beloit, Wis., who is graduating with a master’s degree in civil engineering. Both Bergin and Donovan are in the armed forces: Bergin with the U.S. Navy in Bremerton, and Donovan with the U.S. Air Force at Tyndall Air Force Base in Panama City, Fla.

This is not the university’s first shaking table. A smaller version was built in the early 1970s, but it was underpowered and, says Stanton, “never worked properly.” The new table was built for about $250,000, funded by the National Science Foundation and the UW. By comparison, says Stanton, other tables of a similar size have cost up to $5 million. “We’ve done it mostly because our students have done a super job,” he says.

The new table is anchored by huge bolts to a bed of 2 1/2-feet- thick reinforced concrete which acts as a deadweight while the table jerks its payload back and forth with incredible violence. Each of the four bolts can withstand 55,000 pounds of load.

The floor also acts as a giant test rig to which whole structures or pieces of them, such as a building column, can be bolted while they are subjected to somewhat slower pulling and pushing. Torturing of structures also occurs on a similarly thick L-shaped wall, only here they are not only shaken about but also squeezed downwards with tons of pressure equal to the weight of a building.

Following a period of “tweaking, adjusting and calibrating,” Stanton and his colleagues will begin a number of research projects with the table, including the building of model structures of bridge spans and buildings to see how they react under intense pressure on the table top. Tons of soil in special plexiglass containers will also be shaken vigorously to study seismic effects on the structure of the ground.

Says Stanton, above the roar and grinding of his moving table: “This is quite a day. I feel pretty happy to see it actually move.”

For more information contact Stanton at 543-6057 or on e-mail at {stanton@u.washington.edu}