基于机器视觉的大跨长联桥上无缝线路小阻力扣件纵向服役状态监测研究

Research on longitudinal service condition monitoring of small resistance fasteners on long-span connecting bridge continuously welded rail based on machine vision

以福厦高铁渔溪特大桥为例,提出一种基于机器视觉的小阻力扣件纵向服役状态监测方案,以获取大跨长联桥上无缝线路钢轨纵向变形与复合垫板窜出的时变特征;同时,结合梁轨温度与梁端位移测试结果,分析梁体温度、钢轨温度、梁端累积位移、梁轨相对位移与垫板窜出量之间的相关性。研究结果表明:根据图像识别结果,钢轨在监测阶段将随温度变化产生不同方向的伸缩,且钢轨位移略大于垫板窜出量。钢轨昼夜温差要显著大于桥面气温以及连续梁梁内气温、顶板温度、腹板温度,且梁体温度变化幅度显著比钢轨的小,其原因在于钢轨的比热容较小,在同等热量输入输出时产生的温度变化幅度较大。梁端纵向位移随温度变化幅度较小,最大日位移为0.15 mm;在监测周期内,梁端累积位移呈波动减小趋势,即梁体发生了缓慢收缩,其原因在于夏季到秋季时气温逐渐降低,且最大平均位移变化速率为0.09 mm/d。梁体温度、钢轨温度、梁端累积位移、梁轨累积相对位移和垫板窜出量之间的相关系数均大于0.8,说明其相关性较大,且均呈较好的正相关关系。通过基于机器视觉的小阻力扣件状态监测方法,可见小阻力扣件在福厦高铁渔溪特大桥区段具有较好的纵向服役状态,且监测周期内线路状态均正常,验证了此类方案在小阻力扣件现场监测中的适用性。

The Fuxia High speed Railway Yuxi Extra Large Bridge was taken as an example,and a monitoring scheme based on machine vision for the longitudinal service condition of small resistance fasteners was proposed to obtain the time-varying characteristics of longitudinal deformation of continuous welded rail and leakage of composite pad on long-span connecting bridge;Meanwhile,based on the experimental results of beam rail temperature and beam end displacement,the correlation between beam body temperature,rail temperature,cumulative beam end displacement,beam-rail relative displacement,and the leakage of composite pad was analyzed.The results show that according to the image recognition results,the rail will undergo different directions of expansion and contraction with temperature changes during the monitoring period,and the displacement of the rail is slightly greater than the displacement of the composite pad.The temperature difference between day and night of the rail is significantly greater than the bridge deck temperature,the air temperature in the continuous beam,the top plate temperature,and the web temperature,and the temperature change amplitude of the beam body is significantly smaller than that of the rail,the reason is that the specific heat capacity of the rail is smaller,and the temperature change amplitude is large when the same heat input and output occurs.The longitudinal displacement of the beam end varies slightly with temperature,with a maximum daily displacement of 0.15 mm.During the monitoring period,the cumulative displacement at the end of the beam shows a fluctuating decreasing trend,indicating a slow contraction of the beam body.The reason is that the temperature gradually decreased from summer to autumn,and the maximum average displacement change rate is 0.09 mm/d.The correlation coefficients between the temperature of the beam body,the temperature of the rail,the accumulated displacement of the beam end,the accumulated beam-rail relative displacement,and the leakage of composite pad are all greater than 0.8,indicating a significant correlation and a great positive correlation.By using a machine vision based method for monitoring the condition of small resistance fasteners,it can be seen that the small resistance fasteners have good longitudinal service status in the section of the Fuxia High Speed Railway Yuxi Extra Large Bridge,and the railway line status is normal during the monitoring period,verifying the applicability of this type of scheme in on-site monitoring of small resistance fasteners.