摘要:
针对扁平钢箱梁这一常用的主梁断面形式,为研究其涡激振动性能,并提出有效的涡振抑制措施,以某大跨度钢箱梁悬索桥为工程背景,采用缩尺比为1/50的节段模型进行风洞试验。基于均匀来流风洞试验条件,重点分析研究了风迎角、结构阻尼比和导流板等因素对主梁涡振性能的影响,提出了优化主梁涡振的有效气动措施。研究表明,风迎角的变化会使涡振锁定风速和振幅均产生变化;阻尼比的提高对主梁扭转涡振的抑制比较明显,对竖向涡振的抑制不明显;在主梁风嘴短而钝的情况下,在检修轨道位置安装导流板对主梁涡振的抑制效果不明显,而紧贴风嘴的宽导流板能有效地抑制主梁涡振,且结构形式简单,便于工程应用。
Abstract:
In view of the flat steel box girder which is a commonly used form of main girder cross section,in order to investigate its vortex-induced vibration(VIV)performance,and propose effective mitigation measures,a long span suspension bridge with steel box girder was taken as an engineering example.The section model,whose scale ratio is 1/50,was employed in XNJD-1 (was employed in uniform stream wind tunnel tests).The effects of wind attack angle,damping ratio and guide vane on VIV response were investigated in detail.However,the effects of pave-ment railings and maintenance tracks on VIV response were just briely discussed as on auxiliary research object of this paper,because pavement railings and maintenance tracks are requisite at-tachments to the bridge section in the completion state and large amounts of research results have already shown that the influence of their geometrical modifications and locations on VIV response of the main girder cross section can′t be obviously mitigated.Finally,the effective aerodynamic optimization measures were presented to reduce the VIV response in a series of studies,providing valuable reference for VIV response suppression study for similar bridge section in the future. The research results show that the locked velocities and amplitudes of VIV change with the wind attack angle,and increasing damping ratio can obviously reduce the torsional amplitude of VIV, and less obviously reduce the vertical amplitude of VIV.Removing the pavement railings or maintenance tracks can obviously reduce the amplitudes of VIV and improve the velocities of the first vertical vibration and the torsional vibration,and sometimes even eliminate the VIV response.Above all,the VIV response of this bridge section,whose wind fairing is short and blunt, can be effectively suppressed by installing the wide guide vane at the wind fairing,but the suppres-sion would be ineffective if the wide guide vane is installed at the beam bottom.Furthermore,the structure of this measure is relatively simple so it can be convenient for engineering purpose.
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