| The spiral case with a membrane can resist most of internal water pressure with only a small load being transmitted into the surrounding concrete. This embedding type of spiral case brings convenience of construction, short project duration and low project cost, so it is being applied more and more. For example, some generating units with a unit capacity greater than 700MW adopt this kind of embedding type, including the Three Gorges, Laxiwa and Xiangjiaba hydroelectric power plant in China. Due to these applications, some new problems arise, such as reinforcement calculation of spiral case with a membrane, calculation principle for reinforcement, structural characteristics of stay ring, plane covering range of membrane, etc. Furthermore, with a higher seismicity in recent years, high attention has been given to the earthquake-resistance of hydropower houses located in southwest China with a frequent seismic activity. On account of the aforementioned problems, by means of the finite element method (FEM) using ABAQUS, this dissertation is restricted to the discussion of the following aspects based on some case studies.(1) Both structural mechanics and FEM were used to analyze a spiral case with a membrane, in order to study the influencing factors of reinforcement calculation for it. The influencing factors includeΓ-frame simplification, plane simplification and contact friction between spiral case and concrete. It is concluded that theΓ-frame simplification may cause the calculated reinforcement area to be smaller than needed. It is feasible to simplify a spiral case structure as a plane axisymmetric model in the preliminary reinforcement calculation on condition that the contact friction is considered. It is necessary to take the contact friction into consideration in FEM calculation for spiral case with a membrane, and the friction factor should be defined cautiously.(2) Spiral case structure is classified as non-member bar reinforced concrete structure in the applicable code. It is improper in principle to calculate reinforcement area according to the area of tensile stress figure, which often causes the calculated reinforcement area to be more than needed. The problem of applicable calculation method was illuminated, and the reason for the problem was analyzed specifically. The principle of improving reinforcement calculation was put forward by using FEM. It is confirmed that crack width restriction should be the requirement for the reinforcement of spiral case structure. The case study shows that the damaged range of concrete does not vary remarkably and the increasing ratio of reinforcing bar stress is small, when the partial reinforcement area is reduced. It is proved that the improved calculation principle of reinforcement is effective and operative for reducing partial reinforcement area.(3) In order to analyze the structural characteristics of stay ring on condition that the spiral case and the surrounding concrete jointly resist the internal water pressure, several aspects including stay ring's stress, displacement, deformation and shear capability were studied using three-dimensional FEM, based on a case study of spiral case structure with a membrane. The result shows that great importance should be attached to the stay ring's displacement and deformation other than its structural strength. The membrane's deformation modulus and the friction factor both produce a great effect on the structural characteristics of stay ring. The stay ring resists a great shear, which cannot be ignored in the design of spiral case structure with a membrane.(4) The academia and engineering have not reached a consensus on how to determine a proper plane covering range of membrane for spiral case up to now. Four factors including stay ring's displacement and deformation, stay ring's shear capability, generator pedestal's displacement and deformation, flow channel's torsional strength were considered to solve this problem. The result suggests that if the primary design objective of spiral case structure is to control stay ring and generator pedestal's displacement and deformation, the plane covering end of membrane is suitable to be located between 135°cross section and 180°cross section of spiral case. If the primary design objective of spiral case structure is to enhance stay ring's shear capability and improve flow channel's loading condition, the plane covering end of membrane is suitable to be located between 0°cross section and 90°cross section, or after 270°cross section of spiral case.(5) In order to study the traveling wave effect on seismic response of hydropower house structure with a large plane scale and discuss the effective aseismic measure, a dynamic structural analysis of an actual powerhouse structure was carried out using time-historic analytical method. The result shows that if the earthquake wave speed at the project site is small (smaller than 1000m/s), the traveling wave effect can be taken into consideration properly to make the structural design of powerhouse more reasonable. It is effective to install some viscous dashpots in the surface hydropower house for its earthquake-resistance. The aseismic measure can help enhance the earthquake-resistance capacity of framed bent and powerhouse wall. The supporting height is of great importance to the earthquake-resistance effect of dashpots.
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