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

This paper is the study about the Zipingpu Project that is under construction. Analysis is proposed on large penstocks without expansion joints of the project. The study results are seen as a rule to decide whether the expansion joints can be replaced by the penstocks with soft cushion layer. The major contents and researched results are as follows:1. Begining from the development and application of expansion joints, the developing trend, the status of present research and the existing questions are introduced briefly. Based on a lot of project practice all over the world, the economy and feasibility of canceling the expansion joints are studied.2. As for the Zipingpu Project, a section of penstocks with soft cushion layer is adopted as the replacement of expansion joints. The detailed analysis has been done on stress-strain characteristic of the section of penstocks under the main loads and thermal loads or under the main loads and earthquake loads. The research results proved that it is feasible.3. On the thermal loads analysis, firstly, finite element methods are used to calculate the static temperature field of the penstocks with soft cushion layer and the whole powerhouse during the runtime, including annual average temperature field and static temperature fields in summer and winter. Secondly, calculation of temperature stress has been done as to the temperature ascending condition and temperature descending condition, which are based on the differences between annual average temperature field and temperature field in summer as well as temperature field in winter separately.4. Modal analysis is processed and response spectrum analysis to the structure has been done. In the response spectrum analysis, not only the earthquake load is considered, but also other loads including gravity and water pressure are all considered, for acquiring the practical action of load combination, accordingly the structural condition under dynamic load and the measures of abolishing the expansion joints are demonstrateded more comprehensively.In the end, a summary is given and some problems to be further studied are discussed.