3D Adaptive FEM Analysis Of Arch Dam And Study On Several Stability Criteria

The adaptive finite element method and its application are studied in this thesis.By using the Zienkiewicz-Zhu posteriori error estimator and the correspondingh-version adaptive strategy, the 3D linear elastic adaptive finite element calculation isapplied to three typical examples. Research topics in this thesis also cover theapplication of thrust angle and unbalanced forces theory to the analysis of stabilityand reinforcement of Xiluodu arch dam. The main contents of this thesis aresummarized as follows:In the first part , the theory of error estimation is demonstrated. Analysis showsthat Zienkiewicz-Zhu error estimator based on Super-convergence theory has the bestresult. By using Msc Marc Program , a method for h-adaptive finite element analysisis presented, which is used to estimate the computational accuracy of numericalsolution of finite element analysis. Some conclusions are obtained:(1) The errorestimation and refinement strategy used in this thesis are effective for linear elasticproblems. The adaptive FEM has the advantages of high accuracy and fast rate ofconvergence in solving stress concentration problems;(2) In the mesh refinementprocess, the ZZ posteriori error gets smaller and smaller and finally reaches a constantvalue;(3) For nonsingular area of homogenous material, the adaptive refinementprocess is convergent. The finer the meshes are, the higher the accuracy of FEMsolution is;(4) For different maximum level of mesh refinement, the steadyconvergence error is different. The higher the maximum level of mesh refinement is,the smaller the value of steady convergence error is;(5) For stress concentrationproblem, the maximum level of mesh refinement(the minimum size of element ) shallbe set before the adaptive calculation.In the second part, the stability of Xiluodu arch dam has been analyzed with the3-D non-linear FEM program Tfine. In the calculation the main faults in the rockmass is simulated and the displacements, stress, point safety foctor, and the stabilityof the whole dam in different cases were computed and analyzed.In the third part, the theory of thrust angle and unbalanced forces is studied andapplied to Xiluodu arch dam. some conclusions are obtained :(1) The thrust angle issmaller by elaso-plastic computation than elastic computation. For the non-linearcomputation, the thrust angles at different elevations all increase during overloading,which reveals the internal mechanism of good performance of arch dam in conditionof overloading;(2) The elaso-plastic theory always minimizes the actual unbalancedforces (or reinforced forces) in the sense of a condition number in the norm ofcomplementary energy. Case study for an arch dam shows that the distribution ofunbalanced forces is helpful to evaluate the structural stability and its reinforcement.