基于数字图像处理技术的简支桥墩-梁偏位试验研究

Experimental Study on Pier-beam Junction Deviation of Simply Supported Bridge Based on Digital Image Processing Technology

为了探究量大面广的中小跨径桥梁墩-梁偏位监测困难的问题,提出了一种基于数字图像处理技术的墩-梁偏位计算方法。首先,根据摄像机的内外参数推导了图像像素尺寸与实际物理尺寸的像素尺度因子解析式,通过该解析式建立起图像监测坐标系与实际监测坐标系之间的映射关系。然后,进一步通过摄像头获取偏位前后数字图像,利用数字图像处理技术获取主梁底边特征点偏位前后图像特征点坐标。最后,通过像素尺度因子解析式结合特征角点坐标快速计算出墩梁结合部位的偏位位移量。对上述方法开展了室内模型试验,设计制作了桥梁墩-梁结合部位的模型,通过一个摄像头实现了墩-梁结合部位的图像采集。模拟实际工程中3种墩-梁偏位工况,采集了每种工况的图像,通过该方法得到了每种工况的墩-梁偏位计算值。结果表明:墩-梁偏位测试的平均误差为8.33%,平均误差偏移量为0.652 mm;测试误差与偏位量呈现相关性,偏位量越小误差越大。当偏移量小于5 mm的工况,平均误差为14.06%;偏移量在5~10 mm之间的工况,平均误差为7.75%;当偏位量大于10 mm时,平均误差为3.17%,误差小于5%;该方法具有成本低、维护方便、识别效率高、稳定性好等突出优势,对实际工程中常见的墩梁偏位具有良好的识别效果。

In order to explore the difficulty of monitoring the short and middle-span pier-beam junction deviation of bridges,a method based on digital image processing technology is proposed to calculate the pierbeam junction deviation.First,based on the internal and external parameters of camera,a pixel scale factor analytical formula for the pixel size of the image and the actual physical size is derived,and the mapping relation between the image monitoring coordinate system and the actual monitoring coordinate system is established by the analytic formula.Further,the pier-beam junction digital images before and after deviation are obtained with a camera.Then,the beam’s image feature point coordinates before and after deviation are obtained by using digital image processing technology.Finally,the deviation of the pier-beam junction can be calculated quickly through the pixel scale factor analytical formula and the feature point coordinates.The laboratory model tests are carried out for the above-mentioned methods,a bridge’s pier-beam junction model is designed and manufactured,and a camera is used to capture the image of pier-beam junction.3 kinds of pier-beam deflection are simulated,the images of each condition are collected,and the pier-beam deviation calculation values of each condition are obtained by the method.The result shows that(1)the average error of pier-beam deviation test is 8.33%and the average error offset is 0.652 mm;(2)the test error is correlated with the offset,the smaller the offset,the greater the error,when the offset is less than 5 mm,the average error is 14.06%;(3)the average error is 7.75%when the offset is 5-10 mm,the average error is 3.17%when the offset is more than 10 mm,and the error is less than 5%.The method has advantages,such as low cost,convenient maintenance,high identification efficiency and good stability,etc.,and it has good effects to identify the deviation of piers and beams in practical engineering.