Study On Anti-vibration Design Of Underground Powerhouse Of Hydropower Station

With the planning and construction of a number of large-scale hydropower stations as well as the continuous development of pumped storage power station, the study of dynamic analysis and anti-vibration design of hydropower house are needed in design of many large projects. Taking a large-scale hydropower station as an example, a three dimensional finite element model of the underground powerhouse is established by ANS YS. The anti-vibration performance of the floor slab and the supporting structure are studied in this paper. The main contents include the following three aspects:(1) In order to discuss the influence of structural form and size of floor slab on anti-vibration performance of the structure, models of beam-slab structure, thick-slab structure with the same concrete volume and thick-slab structure with the same static stiffness are established. Based on natural vibration characteristics, dynamic response of the structure under dynamic load of unit, pulsation pressure of spiral case and that of draft tube are studied. The results show that, frequency characteristic of the load is the key factor to affect the dynamic response of floor slab. Under the action of low frequency load, differences between dynamic response of each type floor slab are not obvious. When frequency of load is close to low-order natural frequencies of floor slab, the beam-slab structure can effectively reduce the peak amplitude of floor slab in main vibration area, which shows some superiority. When in high-frequency region, in general, the anti-vibration performance of thick-slab structure is better than that of beam-slab structure.(2) In order to discuss the influencing laws of the constraints of surrounding rock on anti-vibration performance of floor slab, several different constraints on upstream and downstream boundaries of the walls and columns above turbine floor are set. On the basis of analyzing the natural vibration characteristics of the whole structure, low-order modes and frequencies of the floor slab are mainly focused on. Dynamic response of floor slab under dynamic load of unit and pulsation pressure of spiral case are studied. The results show that, changing the constraints of surrounding rock can effectively regulate the natural frequencies of the whole structure, but its effect on the low-order natural frequency of floor slab is not obvious. Under the action of low frequency load, vibrational displacements of floor slab are gradually decreasing with the strengthening constraints. When frequency of load is close to low-order natural frequencies of floor slab, effect of strengthening the restrictions on reducing peak amplitude of floor slab is not obvious. Under high frequency load, the changing rule of dynamic response of floor slab along with the strengthening constraints is different with the load frequency.(3) In order to discuss the influence of thickness of supporting structure on its anti-vibration performance, the outer diameter of supporting structure is increased by 2.0m and reduced by 1.0m form the original model. The three schemes of different thickness were analyzed and compared from three aspects:the natural vibration characteristics, the static and dynamic stiffness of supporting structure and the vibrational response under dynamic load of unit. The results show that, in general, with the increase of thickness, the dynamic and static rigidity of the supporting structure increased and the growth rate decreased, and the optimal thickness should be determined by taking other factors into consideration in anti-vibration design of supporting structure. The influencing laws of the thickness of supporting structure on its dynamic response is related to load frequency and combination mode of load component.