Research On Several Problems In The Revising Of Design Code Of Concrete Arch Dams

The power system standard in China SD 145-85 Design Code for Concrete Arch Dams adopt the allowable stress method, this method ignored the randomicity of action and resistance, adopt single safety factor to measure the safety of arch dams, at the same time conception of safety factor is not specific enough, and have human element factor, adopting limit state design method based on the theory of reliability can conquer the aforesaid disadvantage, comprehensively considered each factor's variability that may effect the reliability of structure, use structural failure probability to measure structural level of reliability, based on different trait of structure to sort and choose safety grade, choose each partial factors reasonably, deal well with the contradiction between structural safety and economy, to realize optimize design, create the condition to choose the best balance between safety and economy.Nowadays, under the support of hydraulic and hydroelectric planning design institute, SD145-85 is being revised according to the related provision of probability ultimate limit state design method, stated in GB 50199-94 United criterion of reliability design in hydraulic and hydroelectric engineering structure. National electric power corporation Chengdu reconnaissance design institute is editor in chief of SD 145-85, moreover Special reports on arch dams was put forward in January 2002. However there are some shortages about standard value of concrete strength, value of partial factors in partial factor design expression and reliability index of arch dams in Special reports on arch dams. According to these reasons, the author collected relative data of home and abroad and carried a series of work on these assets. The results as following:(1) During the revising course of the code, the definition of arch dams concrete strength class must be determined firstly. The determining principle of arch dams concrete strength class disaccord with each other in the related codes of current hydraulic engineering. Aim at this situation, the author discussed the feasibility of arch dams concrete strength class assort with DL/T 5057-1996 code, which focused on standard size of concrete specimen, the infection on dosage of material, the miss judged probability spot check and arch dams concrete wear of elevating concrete strength class assuring rate to 95%, determination curing duration three aspects in this paper. And insisted that it's worth to recommending to take this scheme.(2) Based on the collected arch dams code home and abroad, concrete strength test and other related references, the author put forward a strength standard value scheme that can reflect arch dams concrete strength characteristics. According to principle of GB 50199-94 code, the author gave scheme of all partial factors of ultimate state design expression. The author's calculation indicated that safety level contained by this ultimate state design expression is in good accord with that of allowable stress design expressions in SD 145-85 code.(3) Through comparatively study the current arch dams calculation method of the reliability index found that these methods exist disfigurement and insufficiency in different degree. And given arch dams calculation method of the reliability index based on artificial nerve network and Monte Carlo method, during the course of calculation, discussed how to choose the artificial nerve network 's input parameter under the design checking point is not given, the practical calculation indicated, the choose input parameter method that is given in this paper can simulate the function neighborhood the design checking point, so can advance calculation precision.