CASE STUDY OF BEAM DEFORMATION MONITORING USING CONVENTIONAL CLOSE RANGE PHOTOGRAMMETRY

Abstract

Deformation monitoring is an important procedure of measuring the structural health of completed civil engineering structures. Most traditional methods for measuring deflection occurring in structures require periodic access for designated inspectors to the particular area being monitored. As a remote sensing technique, photogrammetry does not need any contact with the objects of interest, and this can be a great advantage when it comes to the deformation monitoring of inaccessible or simply large structur es. This paper shows a low-cost setup of multiple o ff-the-shelf digital cameras used for photogrammetric 3D object reconstruction for the purpose of deformation monit oring of structural materials. The setup was tested in two e xperiments, where concrete beams were being deformed at different loading conditions by a hydraulic actuato r. The procedures necessary to measure the inflicte d deflections consisted of: image data acquisition, collection of signalized target points, a single bundle block ad justment to establish the relative orientation for the multiple cameras, and a series of multiple light ray inters ections in order to reconstruct the 3D object space coordinates of a se t of sample points for each measurement epoch. The experiments proved that it was possible to detect sub-millimetr e level deflections given the used equipment and se tup.