洪水作用下高速铁路桥梁动力响应研究

Dynamic Response of High-speed Railway Bridge Under the Impact of Flood

为研究洪水作用对高速铁路桥梁结构动力响应的影响,以两跨不等墩高32 m高速铁路简支梁桥为研究对象,建立洪水作用下桥梁下部结构三维水动力分析模型和桥梁有限元模型,获得桥梁下部结构周围流场分布规律与流水压力荷载,探讨了洪水流速、高度和基础冲刷深度的变化对桥梁动力响应和桩基内力的影响规律。研究表明:(1)不同流速的洪水作用于桥梁下部结构时,周围流场的分布规律总体基本一致;(2)当洪水流速大于3 m/s时,下部结构所受的流水压力对桥梁结构的影响不可忽视,且该压力与洪水作用速度及高度呈正相关;(3)基础冲刷深度对下部结构受到的流水压力影响显著,但当承台裸露后,再增大基础冲刷深度时,流水压力增大不明显;(4)桥梁受到洪水冲击时,桥梁的动力响应随时间变化的总体规律基本一致,其响应具体表现为,墩顶横向加速度在冲击时间1.06 s时达到峰值,墩顶横向位移在冲击时间1.16 s时达到峰值,二者达到峰值后呈周期式迅速衰减,墩顶位移、加速度的峰值和最后稳定值以及桩基弯矩均随着洪水流速、高度的增加而增大;(5)随着基础冲刷深度的增加,桥梁动力响应和桩基弯矩均呈增大趋势,但桩基下部负弯矩区受基础冲刷深度影响更敏感。

In order to study the dynamic response of high-speed railway bridge under flood,a two-span high-speed railway simple-supported beam bridge with unequal 32-meter pier height is studied.A three-dimensional hydrodynamic model of the substructure and a finite element model of the bridge under flooding are built up to analyze the law of flow field distribution around and the hydrodynamic pressure.The influences of the change of velocity and height of flood and the foundation scour depth on the dynamic response of bridge and internal force of pile foundation are revealed.The study shows that:(1)The law of flow field distribution is basically the same when the bridge substructure is impacted by the flood with different velocities;(2)When the flood velocity exceeds 3 meters per second,the influence of the hydrodynamic pressure on the substructure cannot be ignored,and the pressure is positively correlated with velocity and height of the flood;(3)The depth of foundation scour has a significant influence on the hydrodynamic pressure.But when the depth of foundation scour is increased after the bearing platform is exposed,the increase of the pressure is not obvious;(4)When the bridge is impacted by the flood,the overall law of the dynamic response of the bridge with time is basically the same.The response is as follows:When t=1.06 s,the lateral vibration acceleration of pier top reaches the peak value;When t=1.16 s,the lateral displacement of pier top reaches the peak value.After the lateral displacement and vibration acceleration reach their peak values,they both tend to attenuate decay rapidly and periodically.With the velocity and height of flood increasing,the peak values and final stable values of displacement and acceleration at prier top as well as the pile bending moment increase;(5)With the increase of foundation scour depth,both the dynamic response and the pile bending moment increase,but the negative bending moment area of pile foundation is more sensitive to the impact of foundation scour depth.