Load test train bridge

The contractual behaviour of a stone bridge close shall be determined with a load test. The train bridge is loaded with up to 6MN (600 tons) which matches 6 locomotives.
Our DIC system Q400 (TU Berlin, Institut für Geodäsie und Geoinformatik) is used to measure the front of the bridge. The natural pattern (stune/splice) is compared between the unloaded and loaded state of the bridge. The pattern comparison ("digital image correlation" measures the displacement of the bridge at all visible points with sub millimeter accuracy. Figure 1 shows the DIC system with the measured bridge surface.

Surphaser at digitisation of the Aller bridgeFigure 1: Q400 system with 3 cameras to measure the brige front.


Figure 2 shows the 100x amplified displacement grid at 4MN load iin the global view camera.


Figure 2: Displacement grid (green=reference state, red=loaded state) at 4MN load. The grid displacement shows the bridge bending 100x amplified.

Figure 3 shows the camera image with the spatially resolved bridge bending along the extracted line at a load of 4MN. Because the load is applied only on the right half of the birdge the deformation is non symmetric. The maximal bending is about 6.3mm at a load of 4MN.
 

 
Figure 3: Color coded displacement and line plot. The color scale shows the bending of the beidge in Millimeter.

 

A few thousand images have been recorded during the whole test at different loads and also in afterwards unloaded states. From these measuremen data the elastic and plastic deformation behaviour of the bridge can be determined.

During the load tests also a laserscanner Surphaser have been used to measure the bridge deformation fullfield from underneath. The measured deformation is identical between DIC and Surphaser. To the application report Aller Bridge-Surphaser.

Summary  

• Measurement system
• Camera resolution
• Number of images:
• Object size
• Data density:

Q400 with 3 cameras for different areas
6MPixel
3500
14 m wide
2000  measurement values per image