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MEASUREMENT OF DEFLECTIONS IN CONCRETE BEAMS BY CLOSE- RANGE DIGITAL PHOTOGRAMMETRY

This paper describes the use of digital photogrammetry for measurement of deflections in concrete beams during destructive testing. A two-video camera system was used to measure vertical deflections with a precision of ±0.25mm (1σ). The system, network design and processing methods are described in detail. Results are presented from several tests of different types of beams. Some of the advantages over contact methods including three-dimensional measurement of deformation components, unrestricted measurement range and immunity to non-linear systematic errors are demonstrated. Comparison is made of photogrammetric and linear-variable-differential transformer deflection measurements.