Study on the Influence of Wind Barrier Porosity on Train-Bridge Coupling Vibration of Heavy-Haul Railway of Rigid Frame-Continuous Beam under Strong Wind
To investigate the effect of wind barrier porosity on the train-bridge coupling vibration of heavy-haul railway of rigid frame-continuous beam under strong wind, the aerostatic coefficients of the train-bridge system were obtained through section model wind tunnel tests when five different pored wind barriers were installed on the bridge, namely 0%, 20%, 40%, 60%, and 100% (without wind barriers). Then the simulation calculation and analysis models of wind-train-bridge coupling vibration were established according to the principle of total potential energy with stationary value in elastic system dynamics. The dynamic simulation calculation and analysis of the wind-train-bridge system for heavy freight trains at different running speeds was carried out by setting the rigid frame-continuous beam bridge with wind barriers at different porosity. The results show that the peak lateral displacement of the bridge significantly decreases with the increase of porosity in the early stage of train operation on the bridge, while the peak lateral displacement of the bridge barely change with the increase of porosity when the train operation tends to fill the bridge. For the dynamic response of trains, the peak value of the train dynamic response increases with the increase of the wind barrier porosity. Compared with fully loaded trains, the dynamic response of unloaded and mix-marshalling freight trains is more sensitive to changes in the wind barrier porosity. Considering the dynamic response of bridge and the evaluation indexes for train running safety (derailment coefficient and wheel load reduction rate), it is recommended to set up a wind barrier with 40% porosity rate for the bridge studied in this paper.
列车编组工况见表2。依据规范将桥址位置1990年—2020年间最大风速换算得到本桥桥面处有车风速范围为30.50~34.98 m · s-1,基于安全考虑选取风速为35 m · s-1。该桥梁设计时速为80 km · h-1,考虑列车位于单线迎风侧、单线背风侧和双线行车3种位置,如图8所示。布置0%,20%,40%和60%透风率和无风屏障共5种风屏障情况下,共计计算45种工况下的车桥耦合振动响应。
当列车分别为空载、混编、满载编组以行车速度80 km · h-1通过桥梁时,主梁跨中横向位移最大值见表3。由表3可知:随着货物列车由空载、混编、满载编组所致列车总轴重的增加,列车迎风工况运行时的跨中横向位移减小,背风工况运行时的跨中横向位移增大,原因在于列车位于迎风工况的偏心荷载效应与横向风荷载效应反向抵消,而列车位于背风工况的偏心荷载效应与横向风荷载效应同向叠加。
单线迎风行车工况下,当列车分别为空载、混编、满载编组以行车速度80 km · h-1通过桥梁时,列车的横、竖向加速度随风屏障透风率的变化如图10所示。由图10可知,列车的横、竖向加速度受风屏障透风率影响不太明显,这是因为作用于列车上的平均风载效应远大于脉动风载效应,车体振动加速度主要由脉动风载效应产生,而脉动风载效应对货物列车而言影响非常有限,故整体而言,风屏障透风率对重载铁路货物列车车体振动加速度影响较小。
当列车分别为空载、混编、满载编组以行车速度80 km · h-1通过桥梁时,列车的轮重减载率和脱轨系数随风屏障透风率的变化如图11和图12所示。
由图11和图12可见:对于空载、满载和轻重混编3种工况,设置风屏障都能够降低列车的轮重减载率和脱轨系数;相比于满载编组列车,空载和轻重混编编组列车的动力响应对风屏障透风率的变化更为敏感,因为满载编组的轴重较大,受到风荷载影响较小,空载编组轴重较轻,受风荷载影响较大;各种工况下,列车的脱轨系数均满足规范要求,而当风屏障透风率达到60%时,轮重减载率超出限值,为了保证列车在本文所分析桥梁在设计速度80 km · h-1的运行安全性,建议桥上设置40%透风率的风屏障。
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