Research On Character Of Long-period Ground Motions And The Response Of High-rise Frame Structure

In recent years, with the development of economy, and the demand of society,long-period structure have sprung up in a large number. Since the pseudo-resonanceeffect, long-period structure is sensitive to long-period ground motion. As a result,anti-seismic study is the urgent problem to solve. However, the characteristic oflong-period ground motion, as well as the failure mechanism of the structure whichsubjected to long-period ground motion. Based on this, the main contents andconclusions are as follows:1. Comparative analysis of the basic characteristics of long-period ground motionand common ground motion. HHT is used to deal with the ground motion, the conceptof strong frequency band, center frequency and time distribution coefficient of energywere proposed. The results show that: long-period ground motion has a largerPGV/PGA and PGD/PGA, the amplitude of the far-field harmonic-like ground motionis minimum, duration is maximum; explain with the time-frequency distribution, theremarkable frequency of the long-period ground motion is smaller, the width of strongfrequency is narrower, and its time distribution coefficient of energy is small.2. Compare the spectrum of long-period ground motion with common groundmotion. the conclusion is that: in long-period bands, the response spectrum oflong-period ground motion is larger than common ground motin, the attenuation of thefomer is much more slowly; the accerleration spectrum has a longer maximum numberrange, the far-field harmonic-like ground motion has special double peak characteristic, the attenuation of the velocity and displacement response spectrum is slow, thedisplacement response spectrum of fling-step ground motion show a tendency ofincrease.3. Select105long-period ground motion and analysis the correlation of its21intesity index and SDOF plastic response, obtain the intesity index of different types oflong-period ground motion which is applicable to period segment.4. By comparing the dynamic response of three frame structures with differentperiods which subjected to three long-period and an ordinary ground motion, reach aconclusion that the long-period ground motions have a significantly influence onlong-period structures. And the corresponding response of far-field harmonic-likeground motion is maximum because of its multiple harmonic-like vibrationcharacteristics.5. in the basis of EMD with which propose the method of setting up the simplifiedequivalent model of velocity pulse based on EMD, with which we can recognizepulse parameters of long-period ground motion, then verify the effective of thismethod through elastic and plastic response spectrum. Analysis the influence of pulseperiod and pulse duration on elastic-plastic earthquake response of a high story framestructure by transforming pulse parameters. Concluded that: with the increase of pulseperiod, the top displacement and the maximum inter story displacement angleincreases, the position of the weak story has a downward trend. it means that thesmaller the velocity pulse is, the more easily of high order mode of long-periodstructure occurs.