Parallel Finite Element Method For Seismic Response Analysis Of Irregular Site

The seismic response analysis of irregular topography is important for the calculation of the seismic responses of structures and the safety valuation of earthquake resistant buildings. Although the three-dimensional (3D) model, based on the direct finite element method (FEM), is ideal for simulating the actual soil situations, the calculating workload largely increases, and common computer hardware is unsuitable. Therefore, parallel finite element method, in order to reduce the calculating workload, is put forward for the seismic response analysis of soil. The main contents in this thesis are listed as follows:1. The feasibility is studied, of using the restrained substructure mode synthesis method to analyze the seismic response of the irregular site. Based on the restrained substructure mode synthesis method and the equivalent linearization method, the practical computer programs of analyzing the seismic responses of soil under uniform excitations are designed. Furthermore, considering the characteristics of the finite element model of soil and the property of the restrained substructure, some improved measures are proposed to increase computer's processing speed.2. Based on the results of numerical experiments, the principle of determining the dimension of the finite element meshes of the soil analysis model under traveling wave excitations is made. Static substructure analysis method is applied to compute the pseudo-static displacements of the seismic response of soil. And the results of numerical examples indicate that it is feasible to utilize restrained mode synthesis method for calculating the response of the irregular topography under traveling wave excitations.3. Neural network technology is applied to study the complicated non-linear relationship between the translation frequency of damping coefficient of soil under earthquake load and its main influence factors. By comparing the calculating results of the seismic response of soil layers in time domain and frequency domain, the way of assembling damping matrix with hysteretic damping coefficients is described. Based on the analysis of the seismic responses of soil layers under several earthquake loadings, the back propagation neural network model is built to predict the values of the translation frequency of damping coefficient. The hysteretic damping is conveniently calculated by implementation of the translation frequency of damping coefficients. And the calculating results of the seismic response of soil layers in time domain are more reasonable on the application of the hysteretic damping.4. The serial programs are developed with the object-oriented language C++, and the related class interfaces are listed. For employing the serial programs to analyze the seismic responses of structures, some examples are made to show the methods of determining artificial boundary and of choosing element type.5. The main types and relative properties of parallel computing system are introduced. Parallel computing environments, such as computer hardware and software requirements, are described. Some concepts involved in parallel computation are explained, and possible problems occurring in the parallel computing procedures are also investigated. Supported by Windows Operation System and Message Passing Interface implementations, the parallel computing programs are developed with C++ language to calculate the seismic responses of the irregular site. Furthermore, the parallel computing programs are tested on high performance computing cluster.6. The seismic response of an actual canyon-shaped site is calculated, and the results indicate that the velocity and direction of the inputting traveling waves affect the peak values of accelerations and phases of the seismic response of the ground surface. For calculating the seismic responses of large-span structures, it is more reasonable to apply multi-supported excitations as the way of input load.