某超高层RC剪力墙结构的实测远场地震反应OA北大核心

The actual seismic response of structures and structural dynamic characteristics under seismic excitation are crucial foundations for seismic analysis and design of structures.Based on the monitoring data obtained from a super-tall building over 160 m in height during two distant earthquakes and environmental excitations,the first two orders of frequencies and the first-order damping ratio were identified using the stochastic subspace identification(SSI)method.The acceleration,velocity,and displacement responses of the structure under earthquake action were analyzed.Compared to environmental excitations,the fundamental period of the structure under seismic excitation lengthens with the increase of amplitude,and the first-order damping ratio significantly increases with the amplitude,and can return back to the pre-seismic values after the earthquake,indicating nonlinear elasticity.Besides,the fundamental period used in seismic design is notably greater than the identified values in the earthquake events,with a relative error exceeding 40％in the short side direction,which is deemed unsafe for seismic design.The identified damping ratios of the structure under seismic excitations are approximately 1.2％and 1.6％in the two principal directions,respectively.These values correspond to the testing results for high-rise buildings in the United States but much lower than the recommended value of 5％for reinforced concrete structures in current Chinese code for seismic design of buildings,suggesting that the damping ratio values recommended by the Chinese codes may be too high.The peak floor acceleration and velocity of the structure during the two distant earthquakes amplify with the increase in building height,with significant contributions from higher-mode responses,and the amplification factors significantly exceed the recommended values in Chinese codes.The seismic displacement response of the structure is characterized by bending deformation,with inter-story drift far less than the code limits.