| In this study, the use of digital close-range terrestrial photogrammetry (DCRTP) for measuring bridge deformations under dead and live load is investigated. A DCRTP system is shown to provide a non-contact, non-destructive means of measurement with the added benefits of digital photography and computer-aided photogrammetry analysis. The fundamental concepts of photogrammetric data gathering and processing are first presented followed by a review of research related to the use of close-range photogrammetry for measurement of structural deformations over the last twenty-five years. Current technologies have progressed to a point where a DCRTP measurement system may be implemented with high accuracy and at a cost competitive with other remote sensing techniques such as GPS, LIDAR, and other laser-based methods.; The study reported herein was conducted in three distinct phases: laboratory testing of a steel beam, evaluation of a prestressed concrete girder bridge (before and after application of dead load), and testing of a noncomposite steel girder bridge under live load. Throughout the project, parametric studies were performed to determine the required number of photographs, the optimal camera positions, and the best layout of tie and control point targets on and around the test structure. Photogrammetric results were compared with those determined from other measurement methods including dial gages, level rods, and curvature-based measurements derived from strain gage data. Theoretical formulas and finite element analyses were used to further validate the photogrammetry results.; Results of the study indicate that double-sided control and tie point targets with uniform distribution throughout the area of the test structure and photogrammetry analysis having more photographs yields the highest accuracy. Improvement, in both the field work (i.e. photographic procedures, target design, target layout, etc.) and office work (i.e. using more photographs, checking of each stage in the photogrammetry solution process, etc.) throughout the three phases of the project ultimately resulted in sub-millimeter accuracy (better than ±1 mm or ±0.039 in) in deflection measurement. |
