Research On The Calculation Of Hydrodynamic Pressure Of Bridge Piers Under Earthquake Action

First of this article,the current situation of deep-water bridge construction at home and abroad,the hazards to bridge buildings when earthquakes occur,and the current status of calculations in domestic and foreign codes has been introduced;theories of hydrodynamic pressure research,including Morison equation,radiated wave theory,and diffraction wave theory,and analysis methods when water interacts with structure and factors affecting hydrodynamic pressure.Secondly,the formulas for calculating hydrodynamic pressure in domestic and foreign norms are sorted out,the project overview of Muluogou Bridge is introduced,and the hydrodynamic pressure calculation model is established for the bridge.Finally,considering the provisions of the four domestic and foreign bridge seismic design codes,the influence of hydrodynamic pressure on the seismic internal force response of bridge piers is studied,and the hydrodynamic pressure of bridge piers under various design parameters such as different section forms,section sizes,pier heights and water depths are calculated.And conducted comparative analysis and research.The main conclusions are as follows:(1)Three superstructure quality conversion methods: additional concentrated mass,uniform load,and concentrated force are used on the top of the pier.By comparing the calculation results with the calculation results of the full bridge,it is found that the quality of the superstructure in the way of additional mass is considered to be the most reasonable.(2)According to the "Code for Seismic Design of Urban Bridges" and "Code for Seismic Design of Japanese Roads and Bridges",the influence coefficient of the pier bottom internal force follows a similar law.The influence coefficient of the pier bottom shear force basically increases according to the linear law with the increase of water depth.The influence coefficient of bottom bending moment basically increases according to the quadratic law with the increase of water depth.According to the 2020 edition of "Code for Seismic Design of Highway Bridges" and "Code for Seismic Design of Railway Engineering",the law of influence coefficient of pier bottom internal force is different from that of urban codes and Japanese codes.the result of.(3)The internal force of the pier bottom caused by the hydrodynamic pressure cannot be ignored.When the water depth is large,the internal force of the pier bottom caused by the hydrodynamic pressure even exceeds the internal force of the pier bottom caused by ground motion alone.Therefore,the seismic design of the bridge must be considered.(4)In terms of considering the influence of hydrodynamic pressure on the internal forces of bridge piers,the "Japanese Road and Bridge Schematic-Seismic Design Code" is the most conservative,followed by the 2020 "Code for Seismic Design of Highway Bridges" and "Code for Seismic Design of Railway Engineering".The "Code for Seismic Design of Bridges" is the least conservative.(5)In most cases,the influence coefficient of the internal force at the bottom of the pier increases with the increase of the pier height.The reason is that with the increase of the pier height,the inertial mass of the pier increases while the stiffness decreases,and the natural vibration period of the pier increases,and the input ground motion is reduced,thereby reducing the internal force of the pier caused by the ground motion.(6)When passing the calculation and analysis of "Urban Bridge Seismic Code" and "Japanese Road and Bridge Show Book-Seismic Design Code",the larger the length-to-width ratio of the rectangular solid pier and the round-end pier,the more obvious the impact of the pier by the seismic water pressure;for the circle Shaped solid pier,the greater the slenderness ratio,the greater the pier will be affected by the seismic water pressure;in the calculation and analysis of the "Code for Seismic Design of Railway Engineering",the larger the size of the bridge pier,the more obvious the impact of the seismic water pressure;When calculating and analyzing the 2020 edition of "Code for Seismic Design of Highway Bridges",the smaller the aspect ratio of the rectangular solid pier,the larger the cross-section size of the circular solid pier,the greater the impact of hydrodynamic pressure.(7)For hollow section piers,attention should be paid to the ratio of internal and external dimensions.The larger the outer section size and inner section size of a rectangular hollow pier are,the greater the additional mass and the greater the internal force at the pier bottom;the larger the external section is,the greater the internal section,the greater the additional mass,and the greater the internal force at the pier bottom.For circular hollow piers,the larger the outer radius,the thinner the wall,the greater the additional mass,and the greater the internal force at the bottom of the pier.