Rocking Earthquake Component And Seismic Analysis Of High-rise Flexible Structure Under Multi-dimensional Earthquake

It has been showed that vertical and tilt ground motion can result in the damage of high-rise flexible structure by earthquakes.Especially,with the development of economy,the heights of buildings become higher and higher,and the lateral stiffness is getting smaller and smaller,so that the influence of vertical and tilt ground motion on the structures would be greater.If their influence are ignored,serious damage might be caused.For now,the recognition of the harmfulness and dangerousness of high-rise flexible structure system under coupled horizontal,vertical,angular accelerations and tilt is insufficient in the earthquake engineering without comprehensive and in-depth research.And the lack of measured records of the rocking earthquake moment also limits the progress of the relevant research to a certain extent.Thus,this paper make a research on the obtain method of rocking earthquake component and the seismic analysis of high-rise flexible structure under coupled horizontal,vertical,angular accelerations and tilt by the methods of theoretical analysis,numerical simulation and shaking table tests.The main research work and conclusions are as follows:(1)Based on the method of frequency-rate and the similarity relation between the Fourier spectrum of the rocking component and that of the velocity of vertical component of ground motion,a method for obtaining the rocking component of ground motion is established by using wavelet transform.Then,the corresponding shaking table tests was designed to verify the reliability of this method.(2)The complete motion equations under coupled horizontal,vertical,angular accelerations and tilt were formed,with exploring the effects of horizontal,vertical ground motion and tilt.The input of vertical ground motion can affect both the geometric stiffness terms and the incentive items of tilt.That the results of shaking table tests and theoretical analysis were basically consistent verified the rationality and accuracy of the complete motion equations.(3)Under coupled horizontal and vertical ground motion,the effects of vertical ground motion on translational response of structures is not obvious,but it would become greater after coupling tilt ground motion,that is,the vertical ground motion can affect both the general and additional gravity second-order effect.Through the comparison between theoretical analysis and shaking table tests,it has been found that the vertical ground motion has a great influence on the additional gravitational second-order effect,and its’ effect 3~5 times the former under the Northridge wave.(4)Compared with vertical ground motion,the effects of tilt ground motion on translational response of structures is much greater.The tilt angular displacement would not only cause the translational response of structures increasing in a large scale,but lead the displacement time history curves of structures to the asymmetric phenomenon of unilateral shift.