Analysis On Stress Characteristics In Concrete Around Shell-Metal Spiral Case＆Cushion Of Hydropower Station

The composite construction of the shell-metal spiral casing in hydroelectric power station is a complex three-dimensional space structure with the three dimensional loading conditions,any result obtained from mechanics of elastic does not precisely describe its stress characteristics. By introducing model of spiral casing designing ,research methods on it is analyzed by knowing developing trend,further expounding different methods on models. Problems on plane strain or stress require no strain or stress at the direction of vertical to plane and loads parallel to the plane,so that the complex three-dimensional space structure simplified as plane during period of poor developed computer is regarded as a trial or a deepening for calculation method of member structure. Results of model test simulating actual designing entity in proportion to certain scale will be put into practice, and this is the main research method afterwards. Three-dimensional computerization really simulates designing entity and load conditions ,so this is an important method and also another casing research method. In the article,spiral casing structure simulated by three-dimensional computerization takes on high imitation ,utility,higher economic benefits,meanwhile it will resolve actual project problems.Characteristics of different material obtained from stress versus strain cure of cushion material are to analyze strain scopes at the respective stress ranges. Devising different test conditions affecting on stresses and strains are further analyzed. Characteristics of High pressure polyethylene plastic with lower froth are better than those of others in material tests,and it will be put into practice.Many factors control cushion thickness. By analyzing Laws of stresses and strains in the concrete under its different thicknesses,it is known that thickness affects extent of stresses and strains. So setting up four models with 0mm,30mm,40mm,50mm in thickness ,quantitative stress and deformation datum obtained from computerization models will resolve reinforcement problems from actual projects ,according as which cushion thickness will be reasonably selected. Changes in the scope of the cushion directly influence stresses and deformation in the its skirt ,specially more obvious in the changing part,so these can explain stresses sensitive to the scope of cushion in the weak part of the concrete. Elastic modulus of cushion is an important index and factor of spiral casing with cushion ,which directly impact on transferring ratio of inner water pressure from metal shell to stress in the concrete. In the computerization models with different thicknesses,all kinds of stress datum obtained by various numbers of elastic modulus can describe relation between these and elastic modulus,in the end,it will be used in the design and research of hydropower station.By three dimensional and part model, its stresses and deformations contract with results of the whole model,and relations between them are known, so provide bases for simplified calculation of feasibility and preliminary phrases. Plane FEM has capability of knowing precision degree of results by member structure method,and contracts with these of three dimensional whole model. Individual load affecting stresses and deformations is analyzed, when the individual load (inner water pressure) applied to the whole model, and so provides stress component for stress superposition under kinds of loads, meanwhile can indirectly analyze effect of another loads on stresses in the concrete.