Study On Response Spectrum Based On Seismic Design Of Structure

Because response spectrum is simple and practical,it has been widely used in many countries as a basic structural seismic design method.Performance-Based Seismic Design is a new concept of seismic design,It has features of multistage fortification target, personality design and flexibility,etc.It is the development direction of the seismic design.This contents of this paper are shown as follows:(1)The comparative analysis of the expression and affecting factors of response spectrum about four countries and regions of China,Japan,the United States and Europe. The difference of Characteristic period,platform value and decaying index of long-period about four countries and regions are analysed.It can be seen that Characteristic period,platform value and decaying index of Seismic Code of China is smaller from comparison of response spectrum for damping ration equal to 5% about four countries and regions.Suggestions of modification about Seismic Code of China are given.(2)Currently, the average value of seismic response spectrum is taken as the fortification level, however,the probability of earthquake fortification level can not be clearly defined.The 368 seismic records of soft soil site are analysed in the paper,and the three-dimensional distributive probability plots of period with variety interval and distributive probability are established.It is shown that,the ratio of every seismic response spectrum and the average is not around 1,so the mean response spectrum cann't reflect the unified fortification level.Thus,the three-dimensional cumulative probability plots are established, and the response spectrum with different probability reliability can be obtained.Finally, the spectrum's expression of provided fortification level and period are fitted.(3)The performance objectives and control method in performance spectra are be revised,and calculation program on the basis of the revision is modified.The elastic and ineastic time history analysis are calculated by modified program for 1085 records.The relationship of the seismic level of seismic design intensity of 8 and the seismic demand of performance spectra of 6 performance levels is analysed.Then performance spectra and the standard seismic design of China are compared.Finally, the influence of reduction coefficient and displacement angle are analysed.(4)In order to research the probabilities levels of performance spectra of average, seismic records of four site are selected for analysis.The three-dimensional distributive probability plots of period with variety interval and distributive probability are established.The mean response spectrum can reflect the characteristics of ground motion very well,but it can not reflect the probabilities levels.Thus,the three-dimensional cumulative probability plots are established,and the performance spectrum with different probability reliability can be obtained.Finally,the performance spectrum's expression of provided probability reliability and period are fitted.