The Research Of Hydrodynamic Response Of Reservoir Dech Arch Bridge Under The Action Of Earthquake

Due to the hydrodynamic pressure,the seismic response of reservoir arch bridge is quite different from that of the ordinary arch bridge(without water),which is located in high intensity area.In order to reduce the arch span or project investment in the project,which often at the expense of increasing submerged depth of arch ring,which is closely related to the hydrodynamic pressure.The seismic response of the reservoir arch bridge is closely related to submerged depth of arch ring and the direction of the excitation.At present,there is less research in this aspect.This paper based on the Yong-chun River Bridge,for analyzing the dynamic characteristics of the arch bridge in the reservoir area under different submerged depth of arch ring.The influence of hydrodynamic pressure on the internal force and displacement of arch ring is studied,and the most unfavorable seismic response of reservoir arch bridge is analyzed.The main research contents and results are as follows:(1)Expound and compare the commonly used hydrodynamic pressure calculation theory,and the calculation formula of hydrodynamic pressure of arch ring is deduced that take into account the influence of the inner domain water(the water inside the arch box).Introduce the finite element theory and the seismic time history analysis theory,the formula of the arch bridge free vibration characteristics is deduced.The Morison equation and Eurocode are used to calculate the hydrodynamic pressure.(2)The influence of hydrodynamic pressure on the self-vibration characteristics of arch bridge under different submerged depth is analyzed.Bridge natural frequency is inversely proportional to submerged depth of arch ring.When submerged depth more than the threshold depth 5f/8(f is rise),the rate of structural frequency reduction is accelerated,and appear the case of mode shape switch to each other.Hydrodynamic pressure mainly affects the low-order mode shape,but the effect on six order mode shape is small.(3)In order to study hydrodynamic pressure on the arch ring the influence law of internal force and displacement,which the seismic analysis of arch bridge under different submerged depth is researched.When submerged depth less than 5f/8,hydrodynamic pressure has little effect on the internal force and displacement of the arch ring.When submerged depth more than 5f/8.the results that using Eurocode to calculate are small and unreasonable,it is recommended to use Morison equation to calculate the hydrodynamic pressure.For the deep-water arch bridge that located in high-intensity areas,it is suggested that submerged depth of arch ring is less than 5f/8.(4)The direction of earthquake excitation and arch ring submerged depth influence on seismic response of the arch bridge are researched,and get the most unfavorable earthquake response of the arch ring internal force and displacement.The analysis shows that 0 °,45 ° and 90 °(the inverse angle with the longitudinal axis of the arch bridge)are likely to be the most unfavorable direction of excitation,depending on the internal force and displacement type of the arch.For the lateral shear force Fr,lateral bending moment Mz.torque and lateral displacement of vault-DY,the most unfavorable excitation direction of the arch bridge is 45°,and the design can be considered at 0 °,but the design value is increased by about 40%.(5)For the reservoir arch bridge that located in high-intensity areas,when submerged depth more than 5f/8,it is suggested that axial compression,vertical shear capacity and torsion property of the arch foot should be strengthened.strengthen the torsion property at 4L/16 section of arch ring(L is clear span),the lateral bending moment capacity at 2L/16 and 5L/16 section of arch ring,the capacity of vertical shear and deformation resistance at vault.