Analysis On Response Of Structures Under Random Earthquake Excitations

Thinking the earthquake action as a random process, and using random vibration theory to study structural response and probability characteristic of structures is a significant development of structural seismic theory. The practical application of random vibration theory is yet very seldom because of its complexity. The purpose of this paper is to combine the complex random vibration theory with the structural seismic knowledge which is very common to most engineers, thus this theory can be accepted and used by everyone.The parameters of Kanai-Tajimi model are studied based on the active building seismic code (GB50011—2001) and the random extreme value theory in this thesis. It is necessary to distinguish the model parameters under frequently occurred earthquake action from the ones under seldomly occurred earthquake action for considering the nonlinear characteristic of the site soil. The corresponding damping ratio and predominant frequency of the site soil under frequently occurred earthquake action are presented. The relation between power spectral factor So and the average value of maximum ground acceleration is derived. The model parameters under seldomly occurred earthquake action are studied preliminarily.Random response of SDOF linear systems and MDOF linear systems to stationary and nonstationary excitations is analyzed in this thesis, and random seismic response spectrum is presented based on the analysis. Spectral value and its probability distribution is also derived. Random seismic response spectrum can make up the defect of normal response spectrum that it can't show the probability of maximum response value. Random seismic response spectrum of elastic-plastic structures is also researched preliminarily.Random vibration theory is the basis of structural dynamic reliability theory. Using random seismic response spectrum to calculate the dynamic reliability is very convenient. It is discovered that the spectral value probability distribution of random seismic response spectra is similar with the first passage failure probability of structural dynamic response. Low cycle fatigue always leads to the failure of structures under ground motion. Dynamic reliability of structures is calculated based on fatigue mechanism in this thesis.