Theory And Applications Of Uniform Seismic Design Spectrum

Since M. A. Biot presented his response spectrum theorem in 1932 and G. M. Housner developed the first seismic design spectrum in 1959, the response spectrum theory and seismic design spectra has been therefore attracting more and more scientists and engineers for further study on and attention to the development of the seismic response spectrum theory and seismic design practice. Near about one century, the theory of earthquake response spectrum and seismic design spectrum have developed and used extensively. The objective of this study is to systematically summarize the theory and its applications of response spectrum, problems as well as possible solutions are considered, and then to propose the theory of uniform seismic design spectrum, which can be used in seismic design of project engineering in different site conditions, magnitudes , distances, and even subground and vertical ground motion situations.Response spectrum, which can present the maximum response of different SDOF systems to a given ground motion component, is an important tool in characterizing earthquake ground motion, and hence is the foucs in the seismic analysis and design of structures and equipment. Seismic design spectra are simplified results and established relaying on characteristics of earthquake acceleration response spectra. However, because the factors that influence response spectra are very complex, it is different to estimate design spectra very specifically, and therefore result in distinct discrepancies and great uncertainties among seismic design spectra of different provisions in the current literature. It is expected for many scientists of the world that the accurate estimation of the seismic design spectra could be obtained only when considerable number of strong motion records are available in future earthquakes and elaborate classification schemes been adopted. On the other hand, some scholars deem that the solution of these problems lie on new approachs, in particular better understanding of the common characteristics of all ground motions rather than waiting for the earthquakes and the accumulation of motion recordings. Hence, much work is needed to identify and quantify common and new characteristics of response spectra and to address issues concerning the special and particular aspects of ground motions.This dissertation aims to provide new knowledge on earthquake response spectra for ordinary and near-fault ground motions after surveying the state-of-the-art work in response spectra of earthquake action provisions in main country and regions. Suggestions on development of guidelines and on future research, as well as limitations of this study are put forward. The investigation of this work includs:1. Based on the theory of structural dynamics, the complete solution, steady state solution and transient solution as well as their respective response spectra of SDOF systems subjected to harmonic ground motions are derived and the relations among these spectra are discussed. The potential effects of harmonic ground motion pulses on structures are considered and the transient vibration should not be ignored in the earthquake resistant design of real structures.2. Bi-normalized response spectrum (BNRS) is defined. The influence of factors such as site condition, distance, magnitude, depth, component direction, etc. on normalized response spectra (NRS) and BNRS are investigated. More than one thousand of strong motion records are selected. Analytical results show that the influence of these factors on BNRS is much slighter and the influence of some of these factor could be ignored.3. Scalar parameters that characterize the frequency content of strong ground motion are used to examine the period characteristics of ground motions during the 1999 Chi-Chi earthquake. The predictive equations of those periods versus fault distance are established. Then, considering the influence of hanging-wall and effect of forward-directivity, period characteristics of near-fault three-orthogonal motion components during the Chi-Chi earthquake are analyzed.4. Based on features of bi-normalized response spectra and frequency periods of earthquake ground motions, considering the influence of damping ratio and the results used in current provisions, unform design spectrum are proposed. Procedures to construct seismic design spectra are considered and devoloped for structural engineering applications.5. Near-fault ground motions are represented by several simple pulses with different waveforms, defined by a small number of parameters. Relationships between pulse amplitudes and pulse period for different pulses and response spectral features of these pulses are discussed. Then the corresponding pulse characteristics of actual near-fault motions are evaluated. Additionally, using the available predictive relationships of parameters and simple pulses, preliminary model for seismic spectra of the near-fault region that includes rupture distance and locate site dependence are developed and discussed.