典型箱梁断面双竖向涡振区的成因分析

Investigation into formation of two lock-in districts of vertical vortex-induced vibration of a box bridge deck section

为研究箱梁断面产生双竖向涡振区的原因,通过同步测振和测压均匀风场风洞试验,基于涡振区的振幅响应与表面压力脉动时程,分析了2个竖向涡振区的振幅与风速关系、表面压力系数均值与均方差值、局部升力与总升力的相关性及局部升力对竖向涡振的贡献。分析结果表明:高风速涡振区比低风速涡振区锁定区间长、振动响应大;低风速涡振区的Strouhal数为0.145,高风速涡振区的Strouhal数为0.082,2个竖向涡振区是由具有不同Strouhal数的2个独立气流涡脱所致;低风速涡振区涡激力主要来源于箱梁上表面中部2道防护栏区域和下表面背压区的气流脉动,高风速涡振区涡激力主要来源于箱梁上表面下游区域和下表面背压区的气流脉动,两者在上表面的气流涡脱相互独立。研究成果对典型钝体箱梁断面有一定的普遍适用性,研究方法可为类似研究提供借鉴。

The formation of two lock-in districts of vertical vortex-induced vibration of a box bridge deck section was investigated via the amplitude response and surface pressure time-histo-ries obtained by synchronizing vibration and surface pressure measurement in the uniform flow wind tunnel test. The relationship between amplitude and wind velocity, means and standard de-viations of surface pressure coefficient, correlation force, contribution of the local lift force to vertical coefficient between local lift force and total lift vortex-induced vibration were studied. The re-suits show that the lock-in district of high wind speed vertical vortex response is wider than that of low wind speed vertical vortex response, and the amplitude of high wind speed vertical vortex response is larger than that of low wind speed vertical vortex response. It is considered that the cause of two vertical vortex shedding response results from two different vortex shedding with a respective Strouhal number of O. 145 and O. 082. Vortex-induced forces of low wind vertical vor-tex response come mainly from the airflow fluctuation at 2 guard rails＇s area of the middle upper surface and back pressure zone of the lower surface, vortex vortex-induced forces of high wind vertical vortex response come mainly from the airflow fluctuation at the downstream zone of the upper surface and back pressure zone of the lower surface, and the vortex shedding at their upper surface are significantly different. The research results have general applicability for some typical blunt box girder sections, and the research methods can provide a reference for similar studies. 1 tab, 9 figs, 15 refs.