Research On The Earthquake Spectra For Site Class Ⅱ

The theory of response spectra is the foundation of seismic design. It is significant to study the response spectra systematically based on the recent earthquake records. Based on 205 earthquake ground motion records collected for site class II, the acceleration, velocity, displacement spectra, input energy spectra, damping energy spectra, hysteretic energy spectra, kinetic energy spectra, elastic strain energy spectra and performance spectra are calculated.In this paper, the major works are as follows:(1) The mean acceleration, velocity and displacement spectra of site class II are calculated. The standard deviations and the dispersion of the earthquake response spectral values are analyzed. The Kolmogorov-Smirnov test (K-S) method with confidence level equal to 0.05 is used to determine the probability density function of elastic-plastic acceleration, velocity and displacement spectra. The proposed expressions of mean elastic-plastic acceleration, velocity and displacement spectra are presented and are proved to fit quite well with the actual response spectra(2) Based on the lognormal distribution derived by the K-S test, the probabilities guaranty of design spectrum in Chinese code are calculated. The results show that the probabilities of some sections in the spectrum are too low and some others are too high. The high frequencies, medium frequencies and low frequencies of the response spectrum in Chinese code are adjusted with different probability guaranty. Compared with the response spectra in Chinese code, the response spectrum derived from the results shows that spectral curve fitted has good probability guaranty and has different dispersion in different periods.(3) The input energy spectra, damping energy spectra, hysteretic energy spectra, kinetic energy spectra and elastic strain energy spectra for site class II are calculated. Besides, the coefficients of variation of the all the energy spectra are calculated and analyzed. (4) The performance targets of acceleration, velocity, displacement for signal degree of freedom systems in time history analysis are determined. According to the methods of performance spectra, the performance spectra are determined by making the high frequencies, medium frequencies and low frequencies of response spectral values reach the performance targets. Performance response spectra with different performance targets in different characteristic periods are compared with response spectra in Chinese code and the mean acceleration response spectra. The performance targets of acceleration are determined over again and the values of performance spectra are debased.