Numerical Analysis Of Large Penstocks Without Expansion Joints And The Static And Dynamic Analysis Of Powerhouses

Two parts of problems are studied in this paper. The first part is about the Three Gorges Project that is under construction. Numerical analysis is proposed on large penstocks without expansion joints of the project. The study result is seen as a rule to decide whether or not the expansion joints can be replaced by the penstocks with soft cushion layer. The second part is about the Paunglaung Hydropower Project located at Burma. The static and dynamic analysis is performed on the underground powerhouse. The project is designed by Norway. And it is necessary to perform the static and dynamic analysis during to the special shape of the supporting structure. The designers adopt the results to improve the design work. The major contents and researched results are as follows:1. Begin from the developing and application courses of penstocks for hydroelectric power station, the developing trend, the existing status of approach and the open question are introduced briefly. Based on some case study in the world, the necessity of installing the expansion joints of the penstocks between the powerhouse and the dam is discussed. The economy and feasibility of abolishing the expansion joints are also been studied.2. For the Three Gorges Project, the section of penstocks with soft cushion layer is adopted as the replacement of expansion joints. The detailed analysis is proposed on stress-strain characteristic of the section of penstocks under the main loads and thermal loads. The research results proved that the longer of the penstock with soft cushion layer, the higher elevation of the concrete in the joint between the powerhouse and the dam, located preformed circular seam on the penstock and retarding it's close time, closing in higher circumstance temperature are all made a contribution to lower the stress-strain state of the penstock.3. Thermal simulating technique is used on the thermal loads numerical analysis, which has break through the conventional method that application of temperature difference load on the structure. The temperature-time and displacement-time curves on the two ends of the penstock with soft cushion layer are obtained by the new technique, which made the research result more reliable and visual.4. The abnormal supporting structure of turbine units, which are composed of a circle beam with three out-of-shape columns, is seldom adopted in the world. According to the static and dynamic numerical analysis results on the whole structure by three-dimensional method, indicated that the stress-strain state isacceptable under the various work condition during construction and operation. And it has no danger to occur resonance vibration with the main vibration sources of turbine units. A project example is proposed for the spread of utility of the new supporting structure of turbine units.Finally, a summary is given and some problems to be further studied are discussed.