Research Of Fluid-structure Dynamic Interaction Of Large Elevated Aqueduct In High Earthquake Intensity Region

Seismic safety of large elevated aqueduct in high earthquake intensity region is an unavoidable challenge during the construction of long-distance water transfer projects in southwest China.There is great fluid-structure dynamic coupling interaction in aqueduct,and its nonlinear characteristics are related to the structural vibration strength,because of the strong regional seismic activity in complex geologic and topographic conditions.Research on the mechanism and influencing factors of fluid-solid coupling dynamic interaction of aqueduct is of great engineering significance,for accurately analyzing the seismic response of structures and ensuring the seismic safety of aqueduct.Relying on the National Key Research and Development Program of China,the engineering data of this paper comes from Yanqing Village aqueduct in the Water Diversion Project in Central Yunnan.Two-dimensional fluid-solid coupling models of the aqueduct body are established based on ANSYS and Fluent software,for the analysis of the characteristics and influencing factors of fluid-solid coupling dynamic interaction of aqueduct,by applying a group of Ricker waves designed with the characteristics of earthquake action.The applicability of the displacement finite element model,the Fluent fluid model and the Housner simplified model is also compared.The main contents and conclusions of this paper are as follows:(1)The hydrodynamic pressure response of the displacement finite element model without fluid damping is the same as that of the Fluent fluid model with the frequency domain method.The hydrodynamic pressure extremums of the undamped model are higher than the Fluent model,but the results of the high-frequency band are very close,with a 3.8%difference,which indicates that the undamped model is an accurate and applicable numerical model.The Housner simplified model can reflect the influence of water body sloshing and aqueduct body vibration characteristics,but it cannot reflect the effect of significant high-frequency components in the artificial seismic wave..The structural dynamic response value of the Housner simplified model is obviously lower than the displacement finite element model,and its dynamic stress extremums of the rod tension,the vertical wall tension and the inner wall compression are 61.0%,49.0%and 50.4%of the displacement finite element model;(2)By Changing the amplitude of Ricker wavelet and artificial seismic wave applied to the Fluent model,the proportion of water surface height caused by fluid nonlinearity is less than 8.0%,and the nonlinearity proportion of hydrodynamic pressure is less than 15.0%,which indicates the nonlinearity of the fluid action in the aqueduct is negligible when water sloshing is limited.The distribution of hydrodynamic pressure is mainly controlled by the water sloshing frequency.When the frequency of wavelet is less than 2 times of the water sloshing frequency,the main way of fluid motion is surface sloshing,otherwise the global inertia movement.When the frequency of wavelet is close to the aqueduct body vibration frequency,the location of the hydrodynamic pressure extremum will move to the surface;(3)According to the results of frequency domain analysis,the fluid-solid coupling dynamic interaction of the aqueduct is mainly controlled by these three factors:the water sloshing frequency,the aqueduct body vibration frequency and the external excitation frequency.The fluid-solid coupling dynamic interaction will be aggravated when the external excitation frequency gets close to the water sloshing or aqueduct body vibration frequency.In the study of this paper,the results show that fluid damping inhibits the dynamic response of the water,but it does not reflect the actual water movement.The effect of fluid compressibility is negligible,and the stiffness of the aqueduct body is the most significant influencing factor of the interaction.The hydrodynamic pressure extremum of the flexible model is 51%higher than that of the rigid model when the excitation frequency is near the aqueduct body vibration frequency,and the hydrodynamic pressure extremum of the flexible model is 62%lower than the rigid model when the excitation frequency is far away from the aqueduct body vibration frequency.