高速列车作用于人行道盖板的脉动风压特性

Fluctuating wind pressure characteristics of sidewalk cover under action of high-speed train

运行的高速列车对线路两侧人行道盖板施加风荷载,盖板可能被瞬时气动吸力掀翻,也可能在列车风的反复冲击下出现疲劳破坏。以32 m简支箱梁桥为工程背景,对CRH380A型高速列车作用于人行道盖板的脉动风压特性进行数值模拟,分析开孔形式、列车运行速度对盖板表面风压和流场分布的影响,阐述盖板开孔“泄压”的作用机理,并基于抗揭安全裕度对盖板进行掀翻风险评估。研究结果表明:盖板上表面离列车近处压强大,风压极值不随开孔数改变;盖板下表面风压分布均匀,风压极值随开孔数增加而增大。开孔能将列车风引入排水渠,让盖板下表面受到与上表面方向相反、数值较小的均匀风荷载,产生一种压强抵消效应,且开双孔效果更好。与其他线路附属结构类似,盖板表面车致脉动风压数值近似与列车速度的平方成正比。盖板抗揭安全裕度随开孔数的增加而增大,随车速的增加而减小,当车速高于350 km/h时,开双孔盖板仍具有充足的安全裕度。

Wind loads will be applied to the sidewalk covers on both sides of the line by running high-speed trains.The covers may be overturned by instantaneous pneumatic suction,or face fatigue failure under repeated impacts of train-induced wind.Taking the 32 m simply supported box girder bridge as the engineering background,the numerical simulation of the fluctuating wind pressure characteristics of the sidewalk cover under the action of high-speed train was carried out.The influence of the opening form,the train speed on the wind pressure,flow field on the surface of the cover was analyzed.The mechanism of the"ventilation"opening was explained,and a risk assessment of the cover being overturned was conducted based on the anti-overturning safety margin.The results show that on the upper surface,the wind pressure near the train is larger,and the pressure extreme values do not change according to the number of openings.On the lower surface,the wind pressure distribution is uniform,and the pressure extremes rise as the number of openings increases.The openings can introduce the traininduced wind into the drain,so that the lower surface of the cover is subject to uniform wind load in the opposite direction to that on the upper surface,with a smaller value,producing a kind of pressure counteracting effect.And the effect of double openings cover is better than that of single opening cover.Similar to the other accessory structure of line,fluctuating wind pressure on the surface of the sidewalk cover is approximately proportional to the square of train speed.The anti-overturning safety margin of cover rises as the number of openings increases,and declines along with the increase of vehicle speed.When the train speed is higher than 350 km/h,the double openings cover still possesses abundant safety margin.