| Popis: |
The objective of the study was to compare and assess suitability of three methods of geodetic measurements used to dynamic testing of suspension bridge. Tachymetry, photogrammetric and laser scanning methods were tested. The above-mentioned methods were tested at the main span of the suspension bridge of 165 m on the Oder River, Poland. Information on the change in the shape of bridge structure under the influence of service load are very significant concerning maintenance (exploitation). The examined bridge comprises 5 spans – four outmost flood spans and the main river span of suspended structure. The structure serves as a technological bridge. Through the bridge passes a belt conveyor connecting lime quarry with a cement factory. Weight of the output transported through the bridge is 900–1100 Mg/h, and the speed of the belt conveyor movement was 2 m/s. The scope of examinations included performing measurements of the changes in the bridge and bearing cable deflection values during the belt conveyor operation and stoppage, using the above-mentioned methods. The most accurate among the used methods was the tachymetry and laser scanning methods, thus the results obtained with these methods were considered as the reference data. The tachymetry measurements were conducted using precise tachymetry TC2002 manufactured by Leica. In the photogrammetric method, digital photography was used, i.e. a Canon 650D camera with high resolution, photographic turntable and the newest software. In the case of the laser scanning, a Trimble TX8 scanner was used. As a result of conducting the experimental tests, the obtained displacements of the bridge did not exceed 49.1 mm and 60 mm for tachymetry (and laser scanning) and photogrammetric method, respectively, thus being lower than the limit values calculated in accordance with the bridge standard. Besides, the bridge displacements obtained under static load were higher than results received from dynamic load. |
