Workers Lift Block-Long Building Off of Its Foundation In Huge Project to Protect Historic Courthouse From Quakes New American Technology Tested In Buffalo Edges Out Foreign Competition

Release Date: November 5, 1993 This content is archived.


SAN FRANCISCO -- When the "big one" hits downtown San Francisco, the historic beaux arts U.S. Court of Appeals Building at Seventh and Mission streets could be one of the safest places to ride it out.

In what may be the largest project of its kind ever undertaken to protect a building from earthquake damage, the block-long historic building is being lifted off of its foundation so that workers can slip an innovative earthquake engineering device underneath.

Once installed, the Friction Pendulum System (FPS) should allow the 60,000-ton building to respond to strong earthquakes by swinging gently from side to side, like a pendulum, minimizing the risk of damage to the structure and the people who work inside it. The system is based on the principle of seismic, or base isolation, which protects structures from earthquake damage by isolating them from ground motions.

Invented, developed and manufactured in the U.S., the system that is being installed was tested extensively at the National Center for Earthquake Engineering Research (NCEER), headquartered at the University at Buffalo.

On the basis of those test results and other measures of its performance, the system was given the highest overall technical score by the technical evaluation board that assessed proposals on behalf of the building's owner, the General Services Administration (GSA). At $2.8 million, the use of the FPS also costs about $4 million less than competing systems developed in New Zealand, Japan and England.

"We put the system through five years of tests at UB and there wasn't a single failure," said Michalakis C. Constantinou, associate professor of civil engineering at UB. "As far as I can see, this system should do very well to protect certain structures in an event where there is extremely strong seismic excitation."

The circa 1905 building is the most ornate federal building west of the Mississippi. Its granite exterior features terra cotta cornices adorned with lions' heads, and red, white and blue glazed brick. Inside, there are hand-painted murals; mosaic tile floors; vaulted, molded ceilings; marble columns and statues, and original fixtures and moldings.

Listed on the National Register of Historic Places, the building is eligible for national landmark status.

While the building survived the great San Francisco earthquake of 1906, it was damaged in 1989 by the Loma Prieta temblor. The GSA closed it immediately to develop methods of repair and to find a way to protect it from future earthquakes.

To select a method of repairing and retrofitting the building, the GSA had engineers and designers consider several devices.

"We were not the leading candidate going in," recalled Victor Zayas, Ph.D., inventor of the FPS and president of Earthquake Protection Systems of San Francisco, which was awarded the GSA contract.

According to Zayas, it was the comprehensive testing done in Buffalo that was a major factor in the GSA's decision.

"The tests and research performed at NCEER were critical in verifying the reliability of the FPS bearings," he said. "Without the NCEER tests, the application of this product to the court building would not have been possible."

At UB, Constantinou and his graduate students subjected models of buildings, bridges and floor systems equipped with the bearings to simulations of historical earthquakes on UB's shake table. They developed the computer codes necessary for evaluating the system's performance on the shake table and provided the experimental data necessary for verifying them. They measured "inter-story drift," the relative displacement between floors; "base shear," the force transmitted to the structure through its foundation, and "bearing displacements" at the friction-pendulum supports installed on the model structure.

The tests showed that the isolators reduced earthquake forces in structures by about a factor of five.

"This is a big step for earthquake engineering technology," said Anoop S. Mokha, Ph.D., a UB graduate and structural engineer with Skidmore, Owings & Merrill of San Francisco, the architectural/engineering firm hired to do the design work on the project.

"The building has a lot of historic features and you want to protect them from damage in future earthquakes," said Mokha, whose doctoral work at UB focused on the system.

The objective was to repair the building and protect it for the future while keeping construction work to a minimum.

NOTE TO EDITORS: Color slides of San Francisco's U.S. Court of Appeals Building and diagrams of the isolators are available from Ellen Goldbaum in the University at Buffalo News Bureau, 716-645-2626.

"We evaluated several options for the location of isolation bearings and types of isolators, to assess their impact on the cost and time necessary for construction," said Navin Amin, chief structural engineer at Skidmore, Owings and Merrill, and leader of the project design team.

"Our devices work very differently from the way that others do," said Zayas. "They work according to the fundamentals of pendulum motion, which is a very predictable and very simple response."

The system is very versatile, Zayas noted, because it uses the characteristics of a pendulum to lengthen the natural period or swinging motion of a structure so that it avoids the strongest earthquake forces. It consists of several parts: a semi-spherical steel slider that is connected at the base of each column in a building; a concave spherical surface on which the slider moves back and forth during an earthquake, and the slider pocket, which houses the bearings and transfers the weight of the building down into the foundation where it is supported.

To install the devices, each of the building's 300-ton steel columns on which the building's foundation rests is lifted by hydraulic jacks. Using flame torches, the workers slice through the conventional steel column, install the FPS and then lower the column back onto the isolator. The installation work is expected to be completed by spring 1994.

In the summer of 1995, when all the retrofit work is complete, the court building will be, by far, the largest and heaviest structure in the U.S. that is equipped to resist earthquake forces using base isolation.

Media Contact Information

Ellen Goldbaum
News Content Manager
Tel: 716-645-4605