| China is located between the two major seismic zones.Earthquake disasters occur frequently,and their suddenness and destructiveness seriously threaten the safety of human life and property.The damage of bridges caused by earthquakes is particularly serious,resulting in incalculable losses.Therefore,we must pay attention to the seismic design of bridges.In particular,the damage of the sulfur ditch bridge caused by the Menyuan earthquake in 2022 is serious,which makes the engineering designers re-examine the seismic design of the beam bridge.The beam bridge includes the simply supported beam and the continuous beam system,which is the main body of the construction and development of railway bridges in China.Among them,the continuous beam is more common with three spans.In China ’s high-speed railway bridge,because the bridge is usually used to guide the road,the beam bridge with common span(main span is less than 128 m)and ordinary pier height(pier height is less than 40 m)is large and wide,and the seismic design is more important.As one of the commonly used seismic isolation devices,viscous dampers are widely used in railway bridges in China due to their advantages of high energy dissipation efficiency,no change in structural stiffness and natural vibration period,stable performance and convenient installation.In this paper,the beam bridge with common span and ordinary pier height under high intensity area is taken as the research object,and the viscous damper is used as the main seismic isolation device to analyze its layout,mechanical parameter value,damping effect and its influencing factors in beam bridge.The main research contents of this paper are as follows :(1)By searching and reading relevant literature,the seismic damage of bridges is summarized.The concept of bridge seismic isolation system is introduced.The commonly used seismic isolation devices and their mechanism of action are introduced.The research status and engineering application of viscous dampers are summarized.(2)Taking the longitudinal seismic response of a 32 m high-speed railway simply supported beam bridge as the research object,the dynamic calculation models of the simply supported beam bridge with equal and variable pier height under two terrain conditions of relatively flat terrain and mountain valley are established respectively.The nonlinear time history analysis method is used to analyze the variation law of the internal force of the longitudinal structure after setting the viscous damper.(3)Taking the longitudinal seismic response of(60+100+60)m high-speed railway continuous beam bridge as the research object,the nonlinear time history analysis method is used to analyze the internal force distribution law and damping effect of the structure under the conditions of two kinds of seismic isolation elements(viscous dampers and Lock-up devices),four layout schemes and four pier heights.(4)Taking the longitudinal and transverse seismic response of(60+100+60)m highspeed railway continuous beam bridge as the research object,the damping effect of the friction pendulum bearing isolation system and the friction pendulum bearing and viscous damper combined system under two pier heights is compared and analyzed.For the combined system,the influence of the longitudinal and transverse unidirectional arrangement and 45-angle arrangement of viscous dampers,ground motion intensity and other factors on the seismic reduction effect of the structure is discussed.Based on the principle of hysteretic energy dissipation,the energy dissipation relationship of the two damping devices is compared and analyzed.Based on the above numerical analysis,the damping effect of viscous dampers under different pier heights,ground motion intensity,arrangement modes and combined use with friction pendulum bearings in high-speed railway beam bridges is systematically summarized,in order to provide reference for the seismic isolation design of railway beam bridges in China. |
