A Method Of Artificial Ground Motion Synthesis That Fits The Peak Velocity And Peak Displacement Of Ground Motion

The collapse of buildings is the major concern of bodily injury and property damage during an earthquake. At present, the earthquake ground motion time history analysis is necessary in the design process, especially in the designs of special structures, such as nuclear power plant, large dams, long span bridges, high rise buildings,etc., to prevent collapse in a large scale earthquake. However,the selection of appropriate earthquake ground motion time history as input is a challenging issue.Different inputs lead to different results. Therefore, the ground motion time history as input of structural dynamic analysis should extensively describe the engineering characteristics of actual earthquake ground motion. In fact, the lack of natural earthquake ground motion records hardly meet the engineering needs. Instead,artificial earthquake ground motion has been widely used because of its ground motion intensity, response spectrum, and duration that easily satisfied the engineering needs.Except for the earthquake response spectrum, other engineering characteristics of earthquake ground motions affect the earthquake response as well. Previous studies have been shown that peak ground velocity and peak ground displacement as inputs have significant effects on the elasto-plastic deformation of structures. Thus, the earthquake response spectrum, the peak ground velocity and the peak ground displacement should be all considered in fitting the input earthquake ground motion time history. In summary,this paper proposed a new wavelet fitting method,which fits target peak ground acceleration, target peak ground velocity, and target peak ground displacement under the premise of fitting the target response spectrum. The main researches and conclusions are summarized as follows:1. Design time history of seismic ground motion in seismic codeFirst of all, all kinds of seismic design specifications and guidelines in China and abroad are collected, the codes of various types of seismic design are introduced in this paper. From the range of the time history analysis, the number of time history and the number of groups of natural history, the peak value of the design ground motions and the characteristics of response spectrum, the duration and correlation of the design ground motions, the similarities and differences of seismic design codes about ground motion time history are compared.Although the response spectrum is an important constraint to determine the input of the earthquakes duration in the various specifications, it is still necessary to fully consider the effect of other characteristics of the ground motion on the structure, especially the ground motion time intensity envelope, peak velocity (PGV), peak displacement (PGD), and non-stationary characteristics.2. Influence of different control parameters on peak velocity and peak displacement discrete levelWhen the acceleration response spectrum is consistent, peak velocity and peak displacement obtained isdiscrete. Based on the statistical principle, when the target spectral cycle is controlled in the case of 6s, to study five control parameters have influence on the dispersion level of the peak velocity and peak displacement, which include the target spectrum characteristic period, the intensity envelope of target spectrum seismic acceleration and the number of target spectrum control period points,"seed" ground motion and site conditions. After statistical analysis, it is considered that these five control parameters have great influence on the dispersion of peak velocity and peak displacement. Therefore, in the process of structural seismic design,not only consider the peak acceleration and response spectrum characteristics of the ground motion,but also focus on the peak velocity, peak displacement characteristics,in order to ensure the safety of the structure in the design process.3. Influence of ground-motionpeakvelocity and peak displacement on non-linear dynamic responses of single-degree-of-freedom systemsIt has been shown that the peak velocity and peak displacement of the input ground motion had an important effect on the seismic response of the structure,especially the elasto-plastic seismic response. For further study, based on the ideal single-degree-of-freedom system (SDOF),the artificial ground motion is synthesized by using the method of superimposing the narrow-band time-history in the time domain as input ground motion, to study the influence of the peak velocity and peakdisplacement on the seismic response of the structure. Through calculating the results of the analysis, it can be seen that the change of the peak velocity and peak displacement of the input ground motion will have a significant effect on the elasto -plastic deformation of the structure for medium and long - period structures.Therefore, in the calculation of the time-history analysis of the elasto-plastic seismic response of such structures, in consideration of the response spectrum characteristics of the input ground motion,it is also important to pay attention to the peak velocity and peak displacement of the input ground motioncharacteristic.4. Artificial ground motion synthesis method for fitting peak velocity and peak displacementWhen fitting the same target response spectrum, the range of peak velocity and peak displacement is large, and the influence of the characteristic period and intensity envelope and other factors on the peak velocity and peak displacement is significant.It has been shown that, in addition to the response spectrum, the peak velocity, the peak displacement and the non-stationary characteristics of the ground motion have a significant effect on the seismic response of the structure, especially the nonlinear response. Therefore, when fitting the target response spectrum, it is necessary to consider the fitting of the target peak velocity and the target peak displacement. On the basis of the previous research,a fitting method based on the wavelet function is proposed to fit the target response spectrum, target peak velocity and target peak displacement. Through the numerical example, this method not only has high fitting precision to the target response spectrum, but also can fit the target peak velocity and target peak displacement according to the precision requirement, also can keep the initial natural ground motion engineering features, meanwhile it can be with a faster convergence rate, and does not appear baseline drift.