Saturday, March 10, 2007

Tech engineer doesn't feel the earth moving under her feet

Argen Duncan El Defensor Chieftain Reporter

A New Mexico Tech engineer is writing computer programs that work with a solution of oil and iron particles to keep tall buildings from collapsing during earthquakes.

Assistant Professor of Civil Engineering Claudia Wilson is developing computer programs that work with the magnetic solution in cylinder-shaped dampers to control the movement of buildings during earthquakes.

Tall buildings have more problems than houses in those situations.

The technology already exists, but Wilson is writing and testing better programs, which determine how much damping to apply to shaking structures.

"And it seems to be working very well," Wilson said.

Next, she plans to use a 3-foot-square "shake table" to test how the computer programs work with model buildings.

"I'm waiting on my shake table to get here," Wilson said.

Wilson plans to start with small steel structures and miniature dampers, but she doesn't know the exact dimensions or appearance of the models. She would like to work with both graduate and undergraduate students.

If her tests go well, Wilson plans to move to larger models, which she can test at several centers.

To work, dampers respond to the computer program, decreasing movement that would bring the building to a bad position or allowing movement that would return it to its original stance.

"It's not making it more flexible, and it's not making it stronger either," Wilson said.

To decrease movement, the program would increase the magnetic field around one area of the cylinder. The iron particles in the solution then form chains, making the fluid stiffer.

It becomes more difficult for the fluid to go through a small passage from one side of the cylinder to the other.

Wilson changes the magnetic field by altering the electrical current in wires wrapped around the passage area.

Wilson needs little current for the change because of the small amount of fluid involved. The dampers could run on a small generator or batteries.

Wilson's computer programs determine how stiff to make the fluid. Sensors measure ground movement and building displacement, and send information to the computer.

During the earthquake, the ground movement and building displacement happen quickly.

"So what I need to do is have the damper reacting just as fast," Wilson said.

The equipment must respond quickly throughout the earthquake, she said.

Other researchers are studying the best number and placement of dampers. Wilson said the devices seemed more effective in the lower part of buildings.

The dampers weigh about 20 tons each, and typically buildings need more than one.

"It would be too expensive, way too expensive, to build a building that's earthquake-proof," Wilson said.

The task would probably be impossible because builders can't predict earthquakes or know from what direction they will come, she continued.

Instead, Wilson said, architects design buildings to perform a certain way.

For small earthquakes, the most common kind, the building should suffer damage only aesthetic aspects, not the structure.

Medium earthquakes should cause little structural damage, only cracking windows or such. In large earthquakes, people should expect damage that may make the building unusable, but the structure shouldn't collapse.

"People are going to have time to evacuate," she said.

Wilson said dampers like the ones she works with are operating in Japan and seem to work well. However, Wilson said, the devices must go through much more testing before use in the United States.

aduncan@dchieftain.com

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