Research On The Visco-elastic Artificial Boundary Model And The Applicability In Complex Foundation

With the development of large-scale hydraulic engineering, nuclear engineering, high rise buildings and other projects, their construction sites scope have been expanded to the complex non rock foundation conditions and high seismic intensity zone. Considering the important effect on the seismic safety of large projects, which is caused by soil-structure interaction, has been the recognition and attention in engineering field, and the time domain analysis method is a current hotspot. In order to achieve on the structural seismic response analysis of complex foundation conditions, considering the calculation accuracy, efficiency and stability in time domain methods, the visco-elastic artificial boundary is chosen to get further studied. The complex foundation structural interaction models and the corresponding wave input mechanisms are established based on it. The engineering applicability of the models and the wave input mechanisms are verified through numerical examples. The main contents are as follows:(1) The two-dimensional and three-dimensional visco-elastic artificial boundary programs are achieved in ANSYS, and the impact of related parameters on the computational accuracy is discussed. Due to the seismic response caused by high frequency seismic waves in soft soil, the model grid division and integration time step settings, which are used to solve the model, are made more detailed numerical analysis, and the corresponding parameters settings are recommended.(2) To a water intake structure seismic response analysis of northeast nuclear power engineering, the model of slope venue is established. Numerical example shows that some numerical problems will be caused while using the seismic input method of visco-elastic artificial boundary to analyze the soil-structure dynamic interaction on the sloping site. The large size difference of side facades on the outer boundary will cause imbalanced horizontal seismic force, which may lead to the divergent results or the drift of displacement. In this paper, based on the basic formula of dynamic interaction and seismic input mechanism, a virtue symmetrical sub-structure system is built to solve those problems. Finally, the accuracy and the stability of the new method are verified through numerical example on the sloping site.(3) To consider the seismic reflection and transmission effect at the material interface in layered soil, combine the seismic reflection and transmission coefficients formulas with the wave input mechanism of visco-elastic artificial boundary, and then dynamic model of layered site and the corresponding wave input mechanism are established. Through comparison with the traditional visco-elastic artificial boundary models by the layered site numerical examples, it is shown that the model and seismic wave input method provide higher accuracy and applicability. And influence by seismic frequency and soil parameters are also discussed, which is beneficial to further understand the dynamic characteristics of layered site and the influence on the nuclear structure.