| Since the reform and opening up,China’s hydropower industry has been developing rapidly,and the hydropower stations built and to be built are scattered all over the country.As an important building in the hydropower station,the stability of the plant structure will have an important influence on the overall stability of the power station.The concrete structures such as spiral case and pier in the plant are large in volume and size.Under the action of various repeated loads,the vibration problem is inevitable.This kind of mass concrete structure bears the continuous effect of vibration load.After a certain period of accumulation,corresponding damage will generate within the structure,causing fatigue damage of partial position.It will affect the normal use of the structure,reduce the stability of the structure,and seriously endanger the safety of the entire hydropower station.Therefore,the study on the fatigue characteristics of the large volume hydraulic concrete structure in the hydropower station,ensuring the long-term stable operation of the hydropower station is a subject worthy of study.Due to the difference of environment and actual size of the structure,the fatigue performance of hydraulic concrete structure is different from that of ordinary concrete structures.At home and abroad,there is little research on the fatigue damage of hydraulic concrete.Therefore,it is necessary to combine the existing fatigue research methods of common concrete structures to analyze fatigue analysis of hydraulic mass concrete structures such as spiral case and turbine pier.Specific research work is as follows:(1)The vibration response of the structure under external loads is analyzed by the time-history method.Time history method is used to get the time course of the structure of the key position,the main tensile stress and the equivalent stress.Through the rainflow counting method,obtain the corresponding stress amplitude and cyclic number.According to the existing research results,the appropriate S-N curve is selected.The damage value is calculated based on the cumulative theory of linear damage and the fatigue time is obtained,which provided a strong basis for the fatigue study of structure.(2)According to finite element method,the whole model of plant structure is established.The simulation objects mainly conclude upstream and downstream wall,floor board,turbine pier,wind hood and spiral case.Combining with machine pier structure natural vibration frequency and range of the unit vibration source frequency,select several different calculationfrequency and apply vibration load of the unit.Time history method is used to carry out dynamic analysis of turbine pier structure.The results show that the higher the calculation frequency of the time history method is,the greater the damage to the corresponding structure is and the shorter the fatigue time is;under the continuous action of the vibration load of the unit,there will be no fatigue damage on the structure of turbine pier.(3)Finite element method is used to establish the monomer model of concrete spiral case.When the concrete volute structure is studied,the maximum pulsating pressure main frequency is selected,and the dynamic response of the concrete spiral case structure under the action of fluctuating pressure is analyzed.According to the calculation results of time history method,the fatigue analysis of concrete spiral case structure is carried out.The results show that under the effect of fluctuating pressure and water pressure,the concrete spiral case structure in use period as a whole will not cause fatigue damage.There may be some fatigue in the local position,but it will not affect the whole structure. |
