Research On Seismic Response Analysis Method Of Dams Based On Quadtree Nonlinear Scaled Boundary Finite Elements

In numerical simulation,the finite element method has become an important tool for analyzing the displacement and stress of dams because of its simple and general advantages.However,because the cells of traditional finite elements are too simple,while the actual analyzed structure is often very complex and the area is huge,resulting in too long time to generate the mesh,and the mesh quality is not high when using traditional finite element analysis.In thesis,the limitations of traditional FEM are addressed by combining the quadtree meshing method with the scaled boundary FEM method to reduce the mesh generation time and improve the computational efficiency while ensuring the accuracy of the simulation.In order to reflect the nonlinear characteristics of the concrete dam material,the nonlinear principal structure relationship is introduced into the quadtree proportional boundary finite element method,and the correctness of the method is verified by the frequency domain time analysis of specific engineering cases,and a numerical simulation method that can be used in engineering practice is established.The main research contents and conclusions of this paper are described as follows.(1)Through least-squares fitting,the form function of traditional finite element is replaced by the form function in scaled boundary finite element,and the nonlinear scaled boundary finite element method is used to perform elastic-plastic analysis on the structural units,and the structural response based on the elastic-plastic theory is obtained by using the Newton-Raphson algorithm after assembling the units.The cantilever beam is used as an example,and its nonlinear scaled boundary finite element model is established,and linear and nonlinear analyses are carried out on it.The results are compared with the finite element,and the horizontal and vertical displacements of the cantilever beam are not much different.(2)The quadtree mesh dissection method is used to divide the structural problem domain into quadtree meshes and extract the mesh information.The extracted mesh information is input into the improved scaled boundary finite element program,and the modal and transient analyses of the structure are performed,and the accuracy of the quadtree scaled boundary finite element method is verified by numerical examples.The results show that,compared with the traditional FEM method,the number of meshes generated is relatively small when using the quadtree scaled boundary FEM method to analyze the structure,which saves computational effort and improves computational efficiency while maintaining the same computational accuracy as that of the traditional FEM.(3)A quadtree-based nonlinear scaled boundary finite element method is used to analyze the modal and time domain nonlinearities of the concrete gravity dam case.The results show that the quadtree-based nonlinear scaled boundary finite element method has strong applicability in practical engineering numerical analysis,and it also shows that this method has flexible mesh editing,can significantly reduce the pre-processing work of the computational model,improve the secondary utilization of the existing model,simplify the tedious data interaction process of traditional engineering design numerical analysis,and improve the degree of automation,thus reducing the computation time and improving the It simplifies the tedious data interaction process of traditional engineering design numerical analysis and improves the degree of automation,thus reducing the calculation time and increasing the calculation efficiency.