Study On Contact Behavior And Vibration Transmission On The Interface Between Steel Spiral Case And Surrounding Concrete In Pumped-storage Power Plants

The construction of Pumped-Storage Power Plants(PSPPs)is one of the major tasks of the construction of the New Power System.Under operating conditions,the contact status of steel spiral case(SSC)and surrounding concrete changes dynamically under various operating internal water pressure(IWP),and it is also subject to seasonal changes in temperature.Moreover,the change of the SSC-Concrete contact status will have a great impact on loadbearing mechanism and dynamic response characteristics of the structure.Accordingly,this thesis investigates the contact behavior and vibration transmission on the interface between SSC and surrounding concrete in PSPPs.The main research contents and research achievements of this thesis are as follows:(1)Focusing on the formation of the initial gap between the SSC and surrounding concrete,the influence of the temperature change during construction period is studied.Based on in-situ measured data of the temperature field,the improved complete simulation procedure(ICSP)is proposed,which can consider the joint effect of the temporary IWP and temperature change from a macro perspective.The initial gap obtained by ICSP agrees reasonably well with in-situ measured data.Furthermore,a three-dimensional nonlinear calculation is carried out to evaluate the structural performance under operating conditions.The results show that the damage values of concrete and the stresses of steel materials are in the safe range under maximum design pressure(MDP).Moreover,the structure still has a high safety reserve when operating IWP reaches 1.6 times of MDP,and special attention should be paid to the area near the inlet of the straight tube.(2)Based on the design philosophy focusing on the safe and reliable operation of pump turbine set,effect of temporary IWP on structural performance is studied,with different design philosophies for temporary IWP considered and compared.The SSC-concrete contact cannot restore the perfect contact-closing status even when the operating IWP is specified to be exactly equal to the temporary IWP,and the contact-closing ratio declines with the increase in temporary IWP.Meanwhile,the seasonal changes in temperature also have a significant impact on the SSC-concrete contact.When temporary IWP is specified to be relatively high according to American design philosophy,the SSC-concrete contact is basically open under normal operating conditions.When temporary IWP is specified to be moderate according to Chinese and European design philosophies,the SSC-concrete contact is more than 40% open under normal operating conditions in winter.(3)The dynamic bearing ratio of the surrounding concrete is in negative correlation with the design of temporary IWP,and it is closely related to the characteristics of the sections themselves.When temporary IWP is designed within the recommended range,the higher the temporary IWP is,the smaller the dynamic bearing ratio of the surrounding concrete.In addition,the seasonal changes in temperature have a profound impact on the dynamic bearing ratio of the surrounding concrete.The stresses of SSC are at relatively low level in all cases,with a high safety reserve,and it is feasible to consider thinning the SSC.The unbalanced hydraulic thrust shared by the thrust ring and the stay ring is in positive correlation with the design of the temporary IWP,and the unbalanced hydraulic thrust shared by the surrounding concrete is in negative correlation with the design of the temporary IWP.The current design philosophy for the thrust ring is proved to be feasible.Moreover,the stay ring actually shares a certain part of the unbalanced hydraulic thrust,and the reliability assessment of the connection between the stay ring and its supporting concrete is,thus,suggested for structural safety.(4)A high precision simulation of fluctuating pressure on guide vanes near vaneless space has little effect on the dynamic response of the structure,and the conventional simulation method is enough to describe the effect of fluctuating pressure in vaneless space.However,a high precision simulation of fluctuating pressure in head cover area has a significant influence on the dynamic response of the structure,and the lack of it will result in smaller dynamic response of the structure.(5)The open status of SSC-concrete contact is beneficial to lower the transmission of fluctuating pressure between the SSC and surrounding concrete,which reduces the vibration displacement,vibration velocity and vibration acceleration of concrete structures.However,it increases the dynamic response of the stay ring and the SSC,which may affect the fatigue life of steel structures.The close status of SSC-concrete contact with contact pressure enhances the transmission of fluctuating pressure between the SSC and surrounding concrete,which is detrimental for vibration resistance of concrete structures.Nevertheless,it reduces the dynamic response of steel structures.(6)The in-situ vibration monitoring and dynamic response analysis of the powerhouse show that,the vertical vibration acceleration near the lifting hole is relatively higher,and results of the dynamic response analysis method considering real SSC-concrete contact agree better with in-situ vibration monitoring data.