Study On The Characteristics Of Far-Field And Long-Period Ground Motion And Structural Response

As a special type of ground motion, the long-period ground motion have significant impact on engineering structure,specially the high-rise buildings, which has been confirmed by a large number of earthquake damage and paid broadly attention in seismic areas. In Japan, Research and engineering practice shows that long-period ground motion is different from long cycle characteristics of response spectrum of ground motion,the problem of the input cannot be settled by improving the designing spectrum of ground motion. There are some regions where exist long-period ground motion and the rapid development of tall building in our country, and the current research exists some problems in quantitative description of the characteristic of long-period ground motion and the determine of designing ground motion, combined with Chinese seismic fortification thoughts and seismic design method. Through the theoretical analysis, data statistics and the structural response analysis, this paper determines the selection criteria of long period ground motion, the characteristics of long-period ground motion and the elastic-plastic response characteristics of high-rise structure by the action of the long-period ground motion.In this paper, the research content:(1) Discribes the standard category of far-field and long-period ground motion;(2) Establishing a long-period ground motion database to screening of seismic wave and analysis the regular;(3) Study the basic characteristic of the long-period ground motion, include the value of the peak(PGA PGV, PGV/PGA), seismic duration characteristics, spectral characteristics and the zero-crossing ratio model employed to describe the non-stationary frequencies;(4) Five high-rise structure models with different cycle is established to analysis seismic motion input and response. While input seismic motion, choice one band of nearfield and short-period ground motion and two bands of far-field and long-period ground motion to disintegrate, and the original ground motion, the long-period and short-period of ground motion to be input for structure respectively. Compares the structural baseshear, interlayer displacement and displacement of the vertices to analyses the difference between long and short-period ground motion, and then to test the rationality of the definite standard of the long-period ground motion.In this paper, the acceleration spectrum average period Tavg is added to classify standards of the far-field and long-period ground motion. And through the study of longperiod ground motion, it was found that the long-period component is very significant. Duration of the long-period ground motion is generally longer than that of the shortperiod ground motion. With the increase of the epicenter, the duration of the long-period ground motion will increase obviously. It is reasonable and effective using crossing-zero rates to describe non-stationary characteristics of earthquake. It can be notified by comparing the base-shear-force and horizontal displacement under long-period and shortperiod ground motion, obtains the following conclusion: as for high-rise building with long vibration period, the structural responses under long-period ground motion is stronger than that under short-period, and the long-period component governs the response.The innovation of this paper are rest with:1) Identify the classification criteria of the far-field and long-period ground motion;2) Study characteristics of the long-period ground motion;3) Decompose ground motion into long-period component and short-period component, then input them to the high-rise building,and study the different structural responses.