Stereovision monitoring of deflection of concrete beam strengthened with ultraviolet-cured glass-fiber reinforced polymer in a destructive test

To monitor three-dimensional structural displacements in civil engineering, a stereovision displacement measurement method based on structure coordinate system is proposed in the present paper, and the absolute displacements of structure can be obtained through establishing the structure coordinate system and coordinate transformation. The center identification algorithm for circular target is studied to acquire the subpixel coordinates of center by combining Canny algorithm and Zernike algorithm. The epipolar constraint is introduced to conduct stereo matching of initial image pairs, and Kalman filtering and neighborhood searching algorithm are both employed to track circular targets on the left and right sequence images. To validate the effectiveness of the proposed method, a destructive test of concrete beams strengthened with ultraviolet-cured glass fiber reinforced polymer is performed in lab. Results show that the load-displacement curves obtained by the proposed stereovision method and linear variable differential transformer agree with each other; this verifies that the proposed stereovision method is feasible and effective for monitoring structural displacement in a destructive test.