Fake Quake to Help Pinpoint Needed Royce Hall Repairs

For the first time in its 65 years as UCLA’s showplace auditorium, people are hoping that the latest Royce Hall production does not bring down the house.

This one is no classical ballet or New Age jazz concert or high-brow stage show, however.

It’s a mock magnitude 4 earthquake designed to show structural engineers where emergency seismic repairs and retrofitting are needed most at the Romanesque performance hall.

Engineers on Friday installed a one-of-a-kind shaking machine inside the heavily damaged building in hopes of causing the brick-and-concrete structure to vibrate enough to show which walls and floors will be most vulnerable in future earthquakes.

A series of accelerometers and seismometers placed throughout the massive building will register its movement as a 10-foot spinner rotates at speeds of up to four revolutions per second.

Officials say they will carefully control the shaking to prevent further damage to the ornate, 1,850-seat auditorium or its six-story towers that form the architectural symbol of the Westwood campus.

“This will be a reality check on a computer model that has been done to predict how the building will perform in an earthquake,” said Gary Hart, a civil engineering professor who designed the $70,000 shaking machine six years ago.

A retrofitting and repair plan is being drawn up by Los Angeles structural engineer John Martin Jr. Although an emergency shoring of the towers has begun, major reconstruction is not expected to begin until the fall.

Hart’s machine, which resembles a huge, one-bladed fan, produces 20,000 pounds of centrifugal force when a 7 1/2-horsepower electric motor sets it spinning. About a ton of weights can be added to the blade to create shaking levels up to that of a magnitude 5 quake. The effect is similar to that of a washing machine on spin cycle that is improperly loaded with soggy clothing and out of balance.

Officials decided to conduct the Royce Hall shaking test after structural engineers praised the value of Hart’s machine in determining seismic strengthening needed for Los Angeles City Hall. It was used in secret tests a year ago to verify a computer-generated analysis of the Downtown tower’s structural weaknesses.

In those tests, the machine was attached to a concrete floor two stories beneath the City Hall tower observation platform. The shaking was done on a weekend when municipal offices were closed, Hart said.

Few people are expected to be inside Royce Hall this afternoon when major testing is scheduled to take place. The machine is bolted to the concrete floor in the former office of Germanic languages department Chairman Ehrhard Bahr. His department’s third-floor facilities in the east tower were badly damaged by the Jan. 17 quake and are partially supported by steel scaffolding.

During a shakedown test of the machine Friday afternoon, few people in undamaged offices at Royce Hall seemed to notice when Engineering Department technician John Langholff revved it up to two revolutions per second.

There was a buzz-saw-like whine from the electric motor, a whup-whup-whup sound from the spinning blade and a modest vibration that registered only slightly on Langholff’s oscilloscope screens.

But it was enough to send Gordon Bradley, an assistant superintendent in charge of outside emergency repairs, running. He warned that columns supporting the towers are sheared off at the sixth floor and that bricks there could fall.

His workers could expect “a little shaking,” Langholff told Bradley.

“But you can assure them it’s not an earthquake.”