Study On Long-period Ground Motion Input And Seismic Response Characteristics For Super High-Rise Building Structures

The stress condition of the super high-rise building(SHRB)is rather complex because of the height,mass and unique modeling.Seismic response characteristics of SHRB also out of the ordinary under different ground motion input,especially those under the far-field long-period ground motion(FFLPGM)that could influence the design and control measures of SHRB to a deeper level.However,it's been a fact that the study of the concept of the LPGM,the engineering characteristics and the strength index of ground motion input and the response characteristics of SHRB under the long-period ground motion is behind the engineering practice.The cognition of the regularity of the LPGM characteristics and the seismic response of SHRB falls behind.Meantime,the application of design response spectrum for SHRB which located in the field that have long period ground motion inoculation mechanism in Japan is also worth to reference.Therefore,this paper has completed some work from three aspects and the achievement is as follows:(1)Definition of the long-period ground motion1)Extraction method of the ground motion long-period component: based on the seismic records of four databases that are corrected by high-pass filter and baseline correction,this paper analyzes the records of Wenchuan Earthquake on the frequency domain and combines the resonance correlation between ground motion and super high-rise structure.Also it proposes the spectral period parameters and determines its value.This paper uses the spectral period parameter limit value to reassemble and correct the IMF component obtained by EMD to obtain the long and short period components of the ground motion.The component separation method is proposed and its rationality and validity are verified.2)Classification of the LPGM: this paper conducts a preliminary judgment on the LPGM from the earthquake source mechanism by the ground motion,magnitude and epicenter distance.Based on the definition of LPGM of near-fault,this paper analyzes the energy ratio(rE)and(PGV/PGA)L characteristic regression of isolated long-period components to obtain the classification model ? of LPGM and conventional ground motion.Combined with PGV of original seismic records and 90% of the energy duration of long period components to distinguish the near-fault pulse-type LPGM,this paper proposes a two-stage definition method of LPGM.(2)Long-period ground motion input1)Characteristics of FFLPGM: in the light of the method given to define three types of ground motions,three basic elements of ground motions,including amplitude,frequency content,and duration,and energy features.Accumulation of crossing zero and variation of instantaneous frequency from Hilbert spectrum are taken into consideration to compare their influence on non-stationary in terms of three types of ground motions by application of SPRC and MATLAB.2)Spectral intensity index: Five models are established by ETABS to compare the difference of the base shear force among the first three vibration modes and the high order modes of which the modal participating mass ratio reaches 90%.Taking the modal participating mass ratio 90% as the control parameter,this paper proposes the spectral intensity index S90 under the effect of the high order mode.The correlation between the S90 and the structural response index is evaluated by Pearson correlation coefficient R.The effectiveness of S90 is evaluated by the IDA-based discrete coefficient ?.3)Seismic response spectrum of FFLPGM for checking: comparing spectrum based on records from Wenchuan Earthquake with seismic design spectrum shows shortages of design SHRB with reference to code for design adopted.Meanwhile,with reference to an opinion that response of SHRB is closely related to velocity and displacement,in combination with FFLPGM of Wenchuan Earthquake and the fitting model put forward by Newmark that three spectral regions by nonlinear fitting to fitting the velocity response spectrum.Then,get the acceleration spectrum for checking by mathematically transformational quasi-relation between velocity spectrum and acceleration spectrum.Then,parameters to standardize the spectrum model of long-period are obtained by Genetic Algorithm.(3)Response characteristics of structure under the long period ground motion inputBy application of ETABS and PERFORM-3D to analyze elastic and plastic responses of SHRB with five different intrinsic periods,comparison of response of SHRB under ground motions categorized by the method mentioned above shows that there are striking differences with reference to different types of inputs,including normal,pulse,LPGMs,indicating that FFLPGMs as special inputs in structural designs of high-rise buildings plays an important role.