倾斜栏杆对流线型箱梁涡激振动性能影响的试验研究

Experimental study on the influence of inclined railings on the vortex-induced vibration performance of a streamlined box girder

涡激振动(VIV)是大跨度桥梁在低风速时易发生的具有强迫和自激双重性质的自限幅风致振动现象,桥面栏杆因其会改变主梁的气动外形而对涡激振动有显著的影响。为了揭示倾斜栏杆对流线型箱梁涡激振动特性的影响及作用机理,采用节段模型风洞测压和测振试验方法,研究不同倾斜角度栏杆对流线型箱梁涡振特性和表面风压的影响,分析了主梁涡振响应、平均和脉动风压分布、局部气动力与涡激力的相关性和贡献系数以及相位差。结果表明:当人行道栏杆内倾时,倾斜角度越大,抑振效果越显著。当人行道栏杆外倾时,外倾10°的主梁抑振效果优于外倾20°的主梁;相比常规的垂直栏杆,栏杆向内倾斜20°和向外倾斜10°有显著抑振效果的原因主要有:主梁上、下表面的脉动风压系数大幅度较低,最多降低了61.54%;在主梁上表面大部分区域,局部气动力与涡激力的相关性系数大幅降低,平均降低了约33.33%;在上表面上游前部和下游尾部及下表面大部分区域的涡振贡献系数均有不同程度的降低;上、下表面各测点间相位差变化的连续性被打断,相邻测点间的相位差更加离散化。

Vortex-induced vibration(VIV)is a kind of wind-induced self-limiting vibration with both forced and self-excited characteristics,which is easy to occur in long-span bridges at low wind speed.The railings and subsidiary facilities of the bridge deck have a significant influence on the VIV performance,as a results of the change in the aerodynamic shape of the main girder.To reveal the influence mechanism of inclined railings on the VIV performance of a streamlined box girder,the pressure distribution and displacement respond of its sectional model were analysed by wind tunnel tests.The VIV response and the mean and fluctuating wind pressure coefficient distribution were comprehensively studied.Meanwhile,the correlation and contribution coefficients,as the well as phase difference between local aerodynamic force and vortex-excited force also were comprehensively studied.The results indicate that when the sidewalk railing is inclined inward,the greater the inclined angle,the more obvious the vibration suppression effect.When the sidewalk railing is inclined outward,the vibration suppression effect of the main beam with 10°inclined outward is better than that of the main beam with 20°inclined outward.Comparing with the conventional vertical railings,the main reasons why the railings inclined 20°inward and 10°outward have obvious vibration suppression effect are as follows:the fluctuating wind pressure coefficients on the upper and lower surfaces of the main girder are considerably lower,decreasing by 61.54%in the most obvious regions;the correlation coefficient between local aerodynamic force and vortex-excited force is reduced by about 33.33%on average in most areas of the upper surface of the main beam;the vortex-induced contribution coefficients are reduced to different degrees in the upstream front,downstream tail and most areas of the lower surface;the continuity of the phase differences between the measurement points are interrupted and become scattered.