Semiactive Base-isolated Structure Subjected To Near-falut Earthquake With Diffirent Motion Characteristics

Earthquake is an inevitable disaster that brings great losses to national economy,life and property of the people.In recent years,with significant development of science and technology,more and more isolation technologies applied to the building structures,in which the base isolation system is the most widely used.However,earthquakes always have different forms,and their impacts on the building structures are very different.Although the supplement of dampers reduces the isolated system's damage against far-field earthquake excitations,it cannot alleviate large pulse transmission caused by the near-fault ground motion.In this paper,a new fuzzy control strategy based on piezoelectric friction damper is proposed for seismic protection of base-isolated buildings,and the damping effect of the semi-active control method against near-field earthquakes of different field sites is studied.The main steps are as follows:(1)The characteristics of the near-fault ground motion which possesses slip effect and the forward directivity effect are studied.Different forms of near-fault ground motions in the database of PEER are selected.Research shows that the slip effect and forward directivity effect of the near-fault ground motion produce obvious velocity pulse of long period.(2)A new fuzzy control strategy based on piezoelectric friction damper is proposed.The dynamic responses of building structures against impulsive ground motion are effectively controlled.The simulation model of the isolated structure is established,the maximum displacement,the maximum inter story displacement and the inter story drift of the isolated structure under far-field and near-fault ground motions are obtained.(3)Based on the displacement,acceleration and story drift of each floor,several function state index are established to compare the damping effects of the non-control,passive and fuzzy control.The fuzzy control strategy proposed in this paper not only can significantly reduce base displacement and acceleration responses,but also can effectively solve the problem of the amplification of the seismic response of the superstructure caused by the traditional free and passive control.(4)The influence of near-fault ground motion with sliding and forward directivity effects on the isolated structure is analyzed based on evaluation index.The relationship between the ground motion parameters and the dynamic response of the structure is also analyzed.The near-fault ground motion with sliding effect is more destructive than far-field earthquake,the correlation between the different parameters of the ground motion and the dynamic response of the structure is different.