大跨度悬索桥竖弯涡振条件下驾驶员行车视线研究

Study on Driver’s Sight Line Under Vertical Vortex-Induced Vibration of Long Span Suspension Bridges

为研究大跨度悬索桥竖弯涡振条件下桥上驾驶员的行车视线,首先,基于传统的风-车-桥耦合振动分析理论,引入桥梁涡激力数值模型,自主编制了涡振条件下风-车-桥耦合振动分析程序;其次,以有3个半波的涡振振型为例,借助几何作图法推导了桥面发生涡振时车内驾驶员视线盲区的计算公式;最后,基于已建立的涡振条件下风-车-桥耦合振动分析程序和驾驶员视线盲区的计算公式,以一座发生竖弯涡激共振的大跨度悬索桥为工程背景,分析了车型、车速和入桥时刻对车内驾驶员视觉盲区最大高度、盲区总持时和盲区占比的影响规律.研究结果表明:驾驶员盲区最大高度呈现周期性变化,其周期约为车辆前进一个涡振半波长度所需要的时间;车速变化不会影响驾驶员盲区的最大高度,但车辆类型不同则驾驶员目高不同,车内驾驶员目高越低,驾驶员前方视觉盲区最大高度也就越高;车重会进一步增加驾驶员前方视觉盲区的最大高度;车辆入桥时刻对驾驶员盲区总持时的影响很小,但驾驶员盲区总持时随着车速的提高而降低;车辆入桥时刻或车速对驾驶员盲区占比的影响小,而车型则对驾驶员盲区占比的影响显著,其中小轿车驾驶员的盲区占比最高(21%左右),大客车驾驶员的盲区占比最小(12%左右).

In order to study the driver’s sight line under vertical vortex-induced vibration(VVIV)of long span suspension bridges,a numerical framework of coupled wind-vehicle-bridge system considering VVIV(termed as WVB-VIWW)is proposed by introducing a vortex aerodynamic model into the traditional coupled WVB theory.Based on the proposed framework and with the aid of geometric construction method,the equation of driver’s blind region under VIVV is derived based on a vortex vibration mode with three half-sine-waves.Subsequently,the proposed WVB-VIVV framework and equation of driver’s blind region are applied to a long span suspension bridge which has experienced VVIV.The influence of several key factors,i.e.,vehicle type,vehicle speed,and the time instant where vehicle enters the bridge,on the maximum height of driver’s blind region,the total time duration of the driver’s blind region,and the ratio of driver’s blind region is investigated.The results indicate that the maximum height of the driver’s blind region varies periodically,and the period is approximately equal to the time required by the vehicle to travel through a half-sine-wave.The vehicle speed has an insignificant effect on the maximum height of driver’s blind region.Because the driver’s sight line height varies with the vehicle type,the lower the driver’s sight line height,the higher the maximum height of the driver’s blind region.Additionally,the vehicle weight could increase the maximum height of the driver’s blind region by increasing the overall deflection of the bridge span.It is also found that the total time duration of driver’s blind region is insensitive to the time instant where vehicle enters the bridge,but the total time duration of driver’s blind region decreases with the increase of the vehicle speed.Furthermore,the time instant where the vehicle enters or the vehicle speed has barely no effect on the ratio of driver’s blind region.However,the vehicle type has remarkable influence on the ratio of driver’s blind region,e.g.,the ratio of driver’s blind region for sedan car and megabus is approximately21%and 12%,respectively.