BUFFALO, N.Y. -- More than two years before it opens its doors -- and who knows how long before it experiences a major earthquake -- University at Buffalo engineering students have determined that San Francisco's new airport terminal building should remain operational during earthquakes registering as high as eight on the Richter scale.
Assigned as a class project, their engineering analysis of a large, longitudinal section of the structure shows that the building -- located less than a mile from the San Andreas Fault and constructed on sliders that may move from side to side by as much as 20 inches during a quake -- will perform as expected.
"This wasn't a textbook problem, it was a real project," said Michael C. Constantinou, Ph.D., UB professor of civil, structural and environmental engineering, who taught the undergraduate structural engineering course.
Constantinou has conducted extensive testing of the innovative earthquake engineering devices that have been installed on the terminal building at the National Center for Earthquake Engineering Research (NCEER) headquartered at UB.
"For this assignment, the students had to figure out how the building was put together and how the devices worked, and then develop models to assess the structure's safety," he explained. "The teams found that it is quite safe."
The building was designed with the expectation that it will sustain virtually no structural damage during strong earthquakes that are typical for this seismically active area.
When completed in the spring of 2000, the terminal will be the largest base-isolated building in the world. Base isolation helps protect structures from earthquake damage by isolating them from ground motions.
"Earthquake engineers have been primarily concerned with the preservation of human life," said Constantinou. "With this building, the owner's goal was to go beyond that, to ensure that the building would not only preserve the lives of people in it, but that it would be strong enough to remain operational even during a major quake."
In addition to the usual peer-review process that all new building designs go through, the UB students' papers have provided project architects and engineers with data that confirms that the stringent safety and performance requirements of the San Francisco Airport Commission have been met.
"The students' results provided us with an independent verification of our design," said Anoop Mokha, Ph.D., associate with Skidmore, Owings & Merrill, a UB graduate and project engineer on the terminal building.
The terminal is a unique, glass-enclosed structure that will contain about 1 million square feet. The massive, wing-shaped roof measures 850 feet by 220 feet, and is supported on only 20 steel columns. The structure is enclosed by a 100-foot-tall glass wall that measures nearly a quarter of a mile long.
Because of the structure's size and complexity, the students analyzed a longitudinal section of the building that will be the most heavily loaded, focusing on structural components, such as roof truss members, columns and braces.
"We were surprised that they could look at this complex structure and figure out how everything worked together," Mokha said, adding that the work of several students was of such high quality that Skidmore, Owings & Merrill may be interested in hiring them.
A unique aspect of the assignment was the fact that the structure stands on sliding bearings.
Before they tackled the airport project, the students had only worked on problems involving structures that stood still.
"When everything stands still, all forces equal zero," explained Al Hanbridge, a UB senior, whose paper was among those sent to Skidmore, Owings & Merrill, and who plans to pursue a career in earthquake engineering.
"But in this case, the structure moves," he said. "That's where it becomes a more complicated analysis."
Victor Zayas, president of Earthquake Protection Systems, which is providing the earthquake-protection devices, said that the system 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.