Performance of a Seismically Isolated Building in the Earthquakes of February 6, 2023, in Türkiye

On February 6, 2023, a devastating earthquake of M7.8 struck Türkiye with an epicenter to the east of the city of Gaziantep. Within hours, it was followed by a M7.5 earthquake some 107 km to the north. The focus of this paper is the performance of a seismically isolated hospital in Adana at distance of 158 km to the east of the epicenter of the M7.8 earthquake. Despite the large distance from the epicenter, the ground shaking was large enough to activate the triple friction pendulum isolators of the building, resulting in a beneficial reduction of accelerations directly above the isolators and avoidance of any structural or nonstructural damage. After baseline correction and filtering of the raw data of the instruments at the hospital, we obtained, by integration of acceleration records, estimates the isolator displacement histories. We performed analysis of the building using properties of the isolators obtained from the production tests on all 1,512 isolators and then adjusting the properties for their 8-year age. Based on comparison of the analysis results and processed records of the building's acceleration and displacement histories, we obtained estimates of isolator properties and confirmed that the isolators primarily responded with motion of the first pendulum (or in Regime I), which is characterized by high stiffness and low friction, leading to some reduction of response in weak seismic ground motion.