UB Engineers Develop Unique Design To Seismically Modernize New Airport Terminal In Istanbul

BUFFALO, N.Y. -- It won't be apparent to passengers landing on today's (Thursday, Jan. 6) inaugural flight at Istanbul's brand new international airport, but the roof of the massive terminal building features a unique approach to seismically modernizing the structure following last summer's devastating quake.

The massive, 800 foot-long by 500-foot-wide roof is the first to feature both the ability to respond to seismic forces as a single, structural unit and the ability to expand and contract in response to exposure to the sun.

The conceptual designs for seismic modernization of the airport were developed by Michael C. Constantinou, Ph.D., professor and chair of the UB Department of Civil, Structural and Environmental Engineering and a researcher with the university's Multidisciplinary Center for Earthquake Engineering Research (MCEER), and colleagues at the University of California at Berkeley and LZA Technology of New York City, the consulting engineers retained to modernize the structure following the magnitude 7.4 quake.

"The structure had only sustained minor damage during the earthquake," said Constantinou, "but considering the certainty with which they expect another large-magnitude earthquake with an epicenter closer to the airport, the desire was to improve the performance level of the structure to one that ensures the safety of people inside, and even beyond that."

The airport was under construction at the time of the quake, which was the main reason it sustained the damage, Constantinou explained.

"Since repairs had to be made, it provided the opportunity to seismically modernize," he said.

According to Constantinou, the third-story columns that support the roof were the most vulnerable link in the existing structure. The objective was to reduce earthquake forces on both the supporting columns and roof.

To increase the building's performance level, he added, the engineers had two options.

"Either we could increase the strength of the building or we could reduce the seismic demand on it, which is not easy to do," he said. "We decided we had to do both."

The modernization scheme consisted of three steps: increasing the strength of the second- and third-story columns by steel-jacketing the columns, seismically isolating the roof to reduce seismic demand on third-story columns and installing "lock-up devices" at roof expansion joints.

The design by Constantinou and his colleagues involved slicing the columns horizontally at the top and installing "friction pendulum" devices manufactured by Earthquake Protection Systems of Richmond, Calif. These devices, which were tested extensively at UB, are designed to allow structures or structural components to swing gently from side to side, like a pendulum.

"This has not been done before," said Constantinou. "What we did was to tie together the segments of this 800-foot-long roof together as they sit on top of these isolation devices. This gives the roof the ability to 'swing' as much as 12 inches with respect to the columns during an earthquake, thus protecting the columns."

At the same time, the roof's direct exposure to the sun necessitated the use of expansion joints that could accommodate thermal movement without inhibiting seismic protection.

The solution came in the form of "lock-up devices" manufactured by Taylor Devices, a Western New York firm that has had a long collaboration with the UB Department of Civil, Structural and Environmental Engineering and MCEER.

Now, instead of having a rigid connection between the roof and the columns, the segments of the building's roof will stay flexible in response to thermal forces, while at the same time featuring an ability to "lock up" as one piece when subjected to earthquake forces. Once activated by seismic activity, the lock-up devices essentially override the expansion joints, allowing the roof panels to respond as a single unit.

This system, as well as the friction pendulum devices, was extensively tested and optimized through collaborations with UB and MCEER.

Constantinou's team was assembled by LZA Technology, which was under contract to the Turkish developer TEPE-AKFEN-VIE and the construction consultant Turner International of New York City to seismically modernize the airport structure.