Researches On Stress Control Criterion Of Arch Dam Design

The stress control criterion is a complex and important topic in arch dam design,and its rationality has a directly relationship with the economy and safety of arch dams.At present in the structure design of arch dams,the major stress analysis methods are arch-cantilever method and finite element method(FEM).Comparing with the arch-cantilever method,FEM has a strong applicability,it can solve many complex problems which cannot be solved by the arch-cantilever method.However its calculation result is largely impacted by the FE mesh,meanwhile,the stress concentration effect is easy to occur near the base surface,which causes some difficulties for making the finite element stress control criteria of arch dams.Finite element equivalent stress method is adopted to solve these problems by the current design specification for arch dams and its design stress control criteria have been maked.However,the linearization assumption of the stress distribution in the finite equivalent stress method does not conform with the real stress distribution law of arch dams.In this dissertation,the cubic equivalent stress method of arch dams has been proposed based on the analysis of the stress distribution law in beam direction and arch direction.Based on analysis of results of four arch dams,i.e.,Xiaowan,Ertan,Yangfanggou,and Zhougongzhai,research on the cubic equivalent stress control criteria are performed,and corresponding stress control indices are proposed.The main content is as follows:(1)The stress analysis methods and the corresponding stress control criteria of the domestic and foreign design specification for concrete arch dams are summaried,the merits and demerits of different analysis methods and the formulation way of stress control indexes are compared,and the cubic equivalent stress control criteria are proposed.(2)The basic theory and process of the finite element analysis are introduced,and a brief introduction of ANSYS finite element analysis is given.(3)The stress distribution law in beam direction and arch direction are analyzed.Then a cubic equivalent stress analysis method of arch dams and calculation steps are proposed based on the least squares fitting polynomial.Based on the case of Xiaowan arch dams,the sensitivity of cubic equivalent stress to FE mesh is studied.The results show that the cubic equivalent stress method can eliminate the grid effect.(4)The finite element analysis model of four arch dams are established by the ANSYS software,the linear elastic finite element analysis under basic load combination is done,and the finite element cubic equivalent stress and finite element equivalent stress of the design specification are calculated.Through comparing with the maximum tensile and compressive stresses between the cubic equivalent stress method and the finite element equivalent stress method,the determination method of finite element cubic equivalent design stress control criteria are put forward.The control indices corresponding to DL/T5346-2006 specification and SL282-2003 specification are proposed.