落石冲击作用下西部山区铁路简支箱梁桥行车安全性研究

Study on Train Running Safety of Simply-Supported Box Girder Bridges in Western Mountainous Areas Under Rockfall Impact

为研究落石冲击作用对铁路桥梁行车安全性的影响规律,以西部山区某铁路简支箱梁桥为研究对象,建立充分考虑材料非线性和接触非线性的落石冲击桥梁仿真分析模型和列车-轨道-桥梁耦合动力分析模型;阐明落石冲击桥墩工况下落石冲击力特征,分析落石冲击作用下桥上行车安全性能,并揭示落石冲击速度、冲击角度、冲击高度和落石直径对行车安全性的影响规律。研究结论如下:(1)落石冲击力的峰值随着落石速度、落石直径的增大而增大,落石冲击高度和冲击角度几乎不影响落石冲击力峰值;(2)落石直径的增大会扩大桥墩结构破坏范围,表现为多个冲击力峰值的出现和冲击力时程的延长;(3)落石冲击速度越快,冲击能量越大,对桥上行车安全影响越大,落石冲击高度越接近墩顶、落石直径越大,列车横向动力响应越大,对桥上行车安全威胁越大;(4)落石冲击角度各工况下列车各项安全评价指标时程曲线变化规律相似,对桥上行车安全影响变化较小;(5)轮重减载率对落石直径和冲击高度十分敏感,轮重减载率在落石直径达到2.5 m时超出规范限值。研究成果可为西部山区铁路桥梁全寿命周期的设计和安全运维提供参考。

In order to study the influence law of rockfall on the train running safety of railway bridges,a simply supported box girder bridge on a railway in western mountainous area was taken as the research object.A rockfall impact simulation model and a vehicle-track-bridge coupling dynamic analysis model,which fully considered material nonlinearity and contact nonlinearity,were established.The characteristics of rockfall impact force on bridge piers were clarified,and the train running safety on the bridge under rockfall impact was analyzed.The influence of rockfall impact speed,angle,height,and rockfall diameter on running safety was also revealed.The results showed that:(1)The peak impact force value of rockfall increased with the speed and diameter of the rockfall,while the impact height and angle had little effect on the peak impact force.(2)The increase in rockfall diameter enlarged the damage range of the pier structure,characterized by the appearance of multiple impact force peaks and an extended impact force time history.(3)The faster the rockfall impact speed and the greater the impact energy,the more significant the threat to train running safety on the bridge.The closer the rockfall impact height was to the top of the pier and the larger the diameter of the falling rock,the greater the lateral dynamic response of the train,posing a higher threat to train safety on the bridge.(4)The variation patterns of the time-history curves of each safety evaluation index of the train under different working conditions were similar across different impact angles of rockfall,with minimal changes in their impact on train safety.(5)The wheel load reduction rate was highly sensitive to rockfall diameter and impact height.The wheel load reduction rate exceeded the standard limit when the rockfall diameter reached 2.5 meters.The research results will provide a reference for the whole life cycle design and safe operation and maintenance of railway bridges in western mountainous area.