Form-finding Of Arms And Analnsis Of Strength And Stability For The Radial Gate With Dendriform Column Arms

The radial steel gate is the most important safety valve in hydraulic structure. It used chiefly in opening or closing water-flowing orifice for controlling water level, adjusting flow, discharging sediment, etc. Its operation conditions have direct relation to the safety of the total hydraulic structures and buildings. With the rapid development of water resources and hydroelectric industry and then improvement of the machine manufacture, the construction scale of hydropower engineering is also expanding, the radial steel gate become more and more big. Surveys show that damages of the radial steel gate are mainly caused by instability of radial arms, so developingnew radial arms with good stability and strong security has great potential applications and significance in science. By using topologic optimization method can get a desired radial arms called dendriform column arms radial steel gate, in which dendriform column arms has reasonable load path, high bearing capacity, and it can effectively reduce the calculation length factors of arms and save material. The new radial arms is superior to traditional arms in both safety and rationality.The theoretical analysis and finite element analysis are comprehensively used in the article, taking deep hole main longitudinal girder radial steel gate effected by even load as its research objective. First, start from the flexural differential equations of the curved beam based on the knowledge of mechanics of materials, the calculation method based on the curved beam theory for the stress distribution of a cross-section is put forward in this article, then the influence on the stress distribution of a cross-section from the curvature of curved beam is analyzed in detail. The simplified models for both traditional two-branches arms and symmetric first order dendriform column two-branches arms are built, combining with the eigenvalue buckling analyses, the form finding analysis of the branch point of first order dendriform column two-branches arms is done. Finally then the stability analysis and static analysis is conducted.The study shows that:(1) The stress distribution in the middle section of radial steel gate with different arms with different radius and included angle is calculated, and the error is analyzed for both straight beam theory and curved beam theory. It respectively uses both straight beam theory and curved beam theory to calculated engineering examples, the results of computation show that the error between straight beam theory and FEM is 15.13%, the error between curved beam theory and FEM is 3.33%. It is can be seen that the calculation precision of the method based on curved beam theory is significantly superior to the calculation precision of the method based on curved beam theory, so the method based on curved beam theory si more safe and reliable.(2) The simplified models for both traditional two-branchs arms and symmetric first order dendriform column two-branchs arms are caculated by the eigenvalue buckling analyses. The result shows that the buckling moment of the simplified model for dendriform column arms is greater than the corresponding value of the simplified model for two-branchs arms in a particular interval, then with increase of the height of trunk, the buckling moment of the simplified model for dendriform column arms firstly increased and then decreased, and it has the highest value at one certain height. As the ratio of the height of trunk to the height of projection of the arm to trunk is about in 0.6~0.8, the buckling moment of dendriform column arms reaches maximum.(3) The radial steel gate with two-branch arms and accordingly the one with dendriform column arms are built,then the static analyses for both two kinds of radial steel gate is conducted, the strength, stiffness and stability of the two kinds of radial steel gate is compared. The results show that the maximum equivalent stress of dendriform column arms is decreased 4.55%, and the stable calculated stresses both around X-axle and around Y-axle are decreased more than 20%. So the stability of radial steel gate is effectively boosted.