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