Seismic Fragility Analysis For Frame-shear Wall High-rise Structure Based On IDA Under Long-period Ground Motions

In the current strong earthquake record data,the near-field long-period ground motion and far-field long-period ground motion are considered to be two kinds of special ground motion.In recent years,the earthquake damage report pointed out that long-period ground motion is more likely to be high and soft Long-period structure damage.In view of the long-period ground motion,China's current building seismic design code does not introduce the corresponding provisions,and the results of the study on the dynamic response of high-rise structures under long-period ground motion are less.Based on the two major strong-motion observation record database of the US Pacific Earthquake Engineering Research Center and the Japan National Research Insitute for Earth Science and Disaster Resiliece,60 near-field long-period ground motions,90 far-field long-period ground motion are selected,another 10 common ground motions are selected in order to enhance contrast,the main research content is as follows:?1?According to the Fourier transform,the selection principle of long-period ground motion is determined,and the reason of the baseline drift in the time-history curves of the ground motion acceleration is discussed.Combined with the existing time-history curves correction method,the solution for long-period ground motion is found,The baseline drift in the time-history curve are processed using baseline adjustment and Buterworth high-pass filtering.The influence of the propagation distance,the construction site condition and the seismic magnitude on the above four basic parameters are discussed around the acceleration peak,the velocity peak,the displacement peak and the predominant period.The results show that the peaks and predominant period of far-field long-period ground motion law change obviously,and the regularity of near-field long-period ground motion is relatively poor.?2?The elastic response spectrum and elasto-plastic response spectrum of the ground motion are obtained by using the bilinear SDOF system.In this paper,the four-type intensity indices are introduced,namely,the acceleration intensity index represented by PGA,the velocity intensity index represented by PGV,the displacement intensity index represented by PGD,and the first periodic spectrum The acceleration index S_a?T₁,5%?is the representative of the intensity index.In addition,taking into account the second performance level of China's seismic code"no unrepairable damage under design-based earthquake"is based on the post-earthquake residual deformation proposed,and further analysis of the intensity index and the residual deformation of the degree.Based on the results of the correlation between the maximum response and the residual deformation,the control parameters suitable for the structural time-history analysis of seismic input under long-period groung motion are proposed.The results show that the elastic response spectra and elasto-plastic response spectra of the two types of long-period ground motion are significantly larger than response spectra of ordinary ground motions in the medium and long periods.When the structure is time-history analyzed,the acceleration-type strength index is suitable for short-period structure,the velocity-type strength index is suitable for medium-period and long-period structures,the displacement-type strength index is suitable for long-period structures,and the spectrum-type acceleration strength index is suitable for short-period,medium-period and long-period structures.?3?Study on the vulnerability of high-rise structures under long-period ground motion.Firstly,a frame-shear wall high-rise structure model is established.Using the traditional incremental dynamic analysis method,the ground motion intensity of the input structure is adjusted in order to obtain the engineering demand parameters of the paper.Then,the structural anti-seismic performance level and the damage level are divided,and the failure probability model under each performance level is determined.Finally,the earthquake vulnerability curves under two types of long-period ground motions are plotted to evaluate the seismic performance of the structure.Based on the failure probability model,the damage probability of the structure is obtained,and the vulnerability index under the action of the frequent earthquake,the fortification earthquake and rarely earthquake are calculated.Combining the experience value of the seismic damage index,The damage degree of the structure is evaluated and the high-rise structure of the frame shear wall designed according to the current seismic code is judged.Under the action of two types of long-period earthquakes,it is necessary to satisfy seismic fortification target of“no damage under frequent earthquake”,“no unrepairable damage under design-based earthquake”and“no collapse under maximum consider earthquake”.The results show that under the same earthquake intensity,the far-field long-period ground motion earthquake demand is the largest in the far field,followed by the near-field long-period ground motion earthquake demand,and the minimum in the common ground motion earthquake demand.The structure is in a state of slight damage when encountering frequently earthquake,fortification earthquake;the structure is in a moderately destructive state when encountering rarely earthquake under the action of two types of long-term ground motions.