Arch Unified Conic Shape Optimization Based On Equivalent Stress Research

The need to electric energy is bigger and bigger in our country. It is a effective method to building hydroelectric power station. In numerous types of dams, engineers are interested in arch dam especially, with its special advantage. The loads which are subject to arch dam are transferred to abutments and basic rock. The dam keeps its stable mainly depends on the reaction of abutments, not by its gravity. There are two advantages of arch dam, one is arch dam need less to concrete material, the other is the overload capacity of arch dam is larger. The sequence of arch dam's curve from good to bad is blending curve, quadratic curve, hyperbola or ellipse, parabola, three center circle, double center circle, single center circle.There are two method used in stress calculation of arch dam optimization. They are try load method and finite element method. The calculation function of finite element method is far stronger than try load method. We can consider the large orifice, complex foundation, gravity abutment, irregular contour, simulation and so on with finite element method. The accuracy of calculation is higher than try load method. With the development of software, finite element method is more and more popular. But when we use three-dimensional elastic finite element, stress concentration will be appear, and the value is often larger than the ensile strength of concrete. But in the actual programme, the inner part of rock exists much fracture, so that the stress concentration is alleviated. To resolve this problem, some scholars of our country put forward "equivalent finite element stress". The principle provides a effective method for software analysis,which is adopted in (SL282-2003) .This paper is based on general finite element calculation software ANSYS8.1, to get a way to fond the best curve of arh dam on unified quadratic curve. First, build finite-element by geometric equation of arch dam with boolean operations of ANSYS; second, arch dam is divided by some certain element in order to build finite element model. In this paper, SOLID95 is adopted to arch dam; SOLID87 is adopted to foundation. They are a kind of quadratic isoparametric element, each node has 3 degree (X, Y and Z direction), which can adaptatde to complex body. But when we calculate structure stress field, we should also calculate stress of temperature field accordingly. In this case we will use "coupled hot and stress" of ANSYS8.1, that is to add a degree to each node as TEMP degree. So each node has four degree that is UX,UY,UZ and TEMP; At last, apply loads to element model, then solve the problem, optimize.At the end of this paper, take Kuai Ze-he arch dam as an example, optimize the shape of the arch dam by the programme originally proposed by this paper. The result enunciation: this programme can alleviate stress concentration effectively and the outcome is economical. This method can shorten the design period, ease the labor strength of engineer.The whole paper is reviewed the knowledge about finite element method and optimization, then we can build the arch dam successfully with the function of ANSYS software. In the process of APDL programme, although the parameters are changed,the optimization circulates smoothly,the entity can glue with each other,meshing correctly. In the ANSYS software APDL programme is embedded. The outcome of a case shows that the APDL programme used in circulating equivalent finite element stress is effective.