Seismic performance assessment of base isolation systems in five hospitals during the M _w 7.8 and M _w 7.6 2023 earthquakes in Southeast Turkey

The February 6, 2023, Kahramanmaraş earthquakes (M w 7.8 and M w 7.6) in Southeast Turkey ruptured a 300 km section of the East Anatolian Fault, resulting in severe ground motions. These two strong earthquakes occurred 9 hours apart and were followed by large‐magnitude aftershocks. Strong ground motions from the Kahramanmaraş earthquakes were recorded by more than 280 strong motion stations. Nine base‐isolated hospital buildings located at distances less than 50 km from the ruptured fault were subjected to strong ground shaking. This paper examines five of the nine hospitals for which seismic isolation designs were available to the authors. The ground motions acting on these hospital buildings were recorded by strong motion stations situated in close proximity. Consequently, the February 6 earthquakes have presented a unique opportunity to assess the seismic performance of base isolation systems during severe earthquakes. All five hospitals were equipped with double spherical sliding (friction pendulum) seismic isolation devices. Subsequently, the authors conducted site visits to the hospitals following the February 6 earthquakes and collected data on maximum and residual response displacements at their isolation levels, as well as on the seismic response of structural and nonstructural components. The maximum response displacements measured at the isolation levels are compared with the maximum displacements calculated by nonlinear response history analysis under the ground motions recorded at the strong motion stations in close proximity to the hospitals.