Seismic Analysis Of Friction Base-Isolated Structure Against Near-Fault Ground Motions

In the far-fault region, the seismic response of the friction base-isolated structure can be reduced significantly. However, the distinct long-duration pulse motion of ground velocity and displacement in the near-fault region may cause the adverse influence on the seismic performance and design of the long-period structure including the base isolation building, and the foundation slab of the base-isolated structure may cause a great slipping, which results in serious damage to the buildings. So it is of great theoretical and engineering significance to study the friction base-isolated structure.The main contents studied in this paper are as follows:Firstly, the concept and the basic characteristics of the near-fault pulse-like ground motions are discussed in this paper. Based on the study of the formation mechanism and the representation of velocity pulse, the near-fault ground motions are simulated by combining recorded ground motions with simple pulses that portray near-fault ground motions. The seismic dynamic responses of the friction base-isolated structure are investigated under the near- field ground motions.Secondly, some typical kinds of friction base-isolated structures are studied: pure- friction base isolation system (P-F), resilient- friction base isolation system (R-FBI) and hybrid damping base-isolated system. The pulse parameters such as pulse type, pulse period and velocity pulse are modified to mark different pulse effect. The influence of different structural inherent parameters on the isolation effects is studied. By comparing to the present code for seismic design of buildings, this paper tries to further perfect the coherent contents of the code. We concludes that these observations are useful in the seismic design of buildings.Thirdly, this paper investigates the seismic response of friction base isolated building pounding with stops under near-fault earthquake ground motions with various impact models. The analytical formulations of the various impact models are outlined, the parameters of these models are studied in detail, and the different factors affecting the pounding response are discussed.Finally, this paper introduces a passive protection measure by locating viscoelasticity buffer. The protection effect of the friction base-isolated structure against near-fault ground motions is studied. The dynamic time history of structures supported on slide-limited friction base isolation system is analysed, the results show that the slide-limited device is effective to reduce the impact response.