For long-term monitoring of the midspan deflection of Songjiazhuang cloverleaf junction on 309 national roads in Zibo city, this paper proposes Zhang’s calibration-based DIC deflection monitoring method. CCD cameras are used to track the change of targets’ position, Zhang’s calibration algorithm is introduced to acquire the intrinsic and extrinsic parameters of CCD cameras, and the DIC method is combined with Zhang’s calibration algorithm to measure bridge deflection. The comparative test between Zhang’s calibration and scale calibration is conducted in lab, and experimental results indicate that the proposed method has higher precision. According to the deflection monitoring scheme, the deflection monitoring software for Songjiazhuang cloverleaf junction is developed by MATLAB, and a 4-channel CCD deflection monitoring system for Songjiazhuang cloverleaf junction is integrated in this paper. This deflection monitoring system includes functions such as image preview, simultaneous collection, camera calibration, deflection display, and data storage. In situ deflection curves show a consistent trend; this suggests that the proposed method is reliable and is suitable for the long-term monitoring of bridge deflection.

The bond-slip relationship for the interface between concrete and carbon fiber reinforced polymer (CFRP) has become a hot research topic. Aimed at the disadvantage of traditional measurement approaches, a stereovision method corrected by epipolar constraint is proposed to measure slip curves of CFRPconcrete interface in the present paper. The proposed stereovision measurement method employs the epipolar constraint to correct digital image correlation (DIC) matching result. The nearest point located on the right epipolar line to DIC matching result is chosen as the new matching point on the right image. Furthermore, this correction method is extended to the sequential matching of right images. The precision comparison test and the detection test of slip for CFRP-concrete interface are performed on the universal testing machine. Results of the precision comparison test show that the proposed stereovision method can improve the measurement accuracy. Experimental results of slip detection of CFRP-concrete interface show that the displacement curves obtained by the proposed stereovision method are in good agreement with that of the linear variable differential transformer (LVDT); this manifests the effectiveness and reliability of the proposed stereovision method, indicating that the proposed stereovision method can be used to measure the entire slip curves of CFRP-concrete interface.

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