基于标志点的多相机数字图像相关方法精度分析及土木工程中的应用

Precision analysis and civil application of multi-camera digital image correlation method based on encoded targets

为实现土木工程构件的高精度全场变形测量,分析了基于标志点的多相机测量方法的实际精度,并将该方法用于BFRP筋海水海砂珊瑚-UHPC组合梁的抗弯实验.利用编码标志点对多套双目系统的结果进行坐标统一,并通过引入拼接误差u_(n)对多相机测量结果的坐标统一精度进行定量评估分析.实验结果表明:面内位移量较小时,拼接误差u_(n)基本等同于双目系统自身的匹配误差水平,随着位移量增大,u_(n)随之增大;拼接误差的标准偏差σ_(u)始终在0.01 mm内波动,且位移量最大时拼接误差的均值u-与实际位移的相对误差仍小于0.03%,多套测量系统的坐标系统一精度满足工程需求;对于混凝土组合梁的全场位移和应变场的测量,局部位移数据与位移计数据基本吻合.多相机数字图像相关方法可以大幅提高变形测量分辨率,适合在大型土木工程构件变形测量中推广运用.

To achieve high-accuracy,full-field deformation measurement of civil engineering structures,the accuracy of the targets-based multi-camera measurement method was analyzed,and the method was applied to the bending test of seawater sea-sand coral-ultrahigh-performance concrete(UHPC)composite beams reinforced with basalt fiber-reinforced polymer(BFRP)bars.Coding targets were used to u_(n)ify the coordinates of the results of multiple binocular systems,and the stitching error u_(n) was introduced to quantitatively evaluate and analyze the coordinate u_(n)ification accuracy of the measurement results of multiple cameras.Experimental results show that when the in-plane displacement is smaller,the stitching error u_(n) is basically equal to the matching error level of the binocular system,and u_(n) increases with the increase of the displacement.The standard deviation of the stitching errorσ_(u) always fluctuates within 0.01 mm,and the relative error between the mean of the stitching error u-and the actual displacement is always less than 0.03%when the displacement is maximum,indicating that the u_(n)ified precision of the coordinate system in multiple measurement systems meets the engineering requirements.For the measurement of the whole field displacement and the strain field of the concrete beam,the displacement measurement data are basically consistent with the displacement meter data.The multi-camera digital image correlation method can improve the resolution of the deformation measurement,thus promoting the deformation measurement of large civil engineering components.