ABSTRACT
The objective of the study was to compare and assess suitability of laser scanning method to determine geometric changes of the bridge structures. The laser scanning method was tested at two suspension bridges. First was a technological bridge (Chorula, Poland) with effective main span of 165 m, and second one was a historic cast iron bridge (Ozimek, Poland) with span of 27.7 m. The first measurements were conducted using a FARO Focus 3DX130 scanner. In the case of the second bridge (Ozimek), the results clearly indicate that reduced the distance to the bridge (40 m) allows to obtain satisfactory results, i.e. a full inventory of the bridge elements. Taking into account the above experience, the authors decided to use for the technological bridge examinations a Trimble TX8 scanner. It turned out that the Trimble TX8 scanner allows to obtain the technological bridge displacements under static loads. For the results analysis and point cloud pro-cessing, specifically designed the Trimble Real-Works 10.2 program was used. The software provides a complete solution to efficiently register, analyse, model and create deliverables using data from virtually any source. The software also allows for the automatic interpolation of the markers centre, which in this study constituted the measurement targets and white reference spheres (the same as in the photogrammetric method). The subsequent scans are matching to characteristic points (measurement targets and white reference spheres) in such a way that the next measurement sessions can be topologically consistent. This allows for significantly reduction of the working time on the measurement object. The obtained results were verified by the tachymetric method using the TC 2002 instrument. The presented approach to the bridge testing using scanner method can help in the bridges diagnostic, especially in the case there are not the technical project, for example for old bridges.
