Study On Bi-Normalized Earthquake Velocity Response Spectra

Since the theory of response spectrum was presented, it has been widely used in the seismic code all over the world. It is significant to study response spectrum for improving the reliability of seismic code. The seismic design spectra are established based on the characteristics of earthquake acceleration response spectra, together with consideration of experiences and economy. The seismic design spectra are affected by a lot of factors, such as site conditions, magnitude, distance to epicenter, etc. It is much difficult to give one kind of seismic design spectra for each possible case. In order to solve the problem mentioned above, it is a new way to study the common characteristics of earthquake response spectra, and investigate the new features of response spectra. The main works of this study are summarized as following:(1) Four kinds of periods are defined to normalize the velocity response spectra, and then the bi-normalized velocity response spectra (BNVRS) are investigated for different site conditions. The best period are selected out for normalizing the velocity response spectra.(2) With a great number of ground motions, the BNVRS are compared with the normalized velocity response spectra (NVRS). The conclusion is reached that the BNVRS have much better regularity and consistency than NVRS.(3) The characteristics of BNVRS and bi-normalized acceleration response spectra (BNARS) are studied for different period ranges, and an experimental formula is given for the two kinds of spectra. Additionally, a new seismic spectrum is proposed based on the BNVRS and BNARS, which are compared with the design spectra in Chinese seismic code.