Indicators of civil engineering material during load tests

Project title

Indicators of civil engineering material during load tests

Funding

Funded by Federal Office for Building and Regional Planning (BBR)

Aims

The aim of this approach is the development and empirical examination of special indicators for load tests for a better evaluation constructions.

Flexible photogrammetric methods should be applied to detect displacements on a test specimen surface. The analysis of the image sequence should be automized and a real-time analysis should be realized during a load test.

Experimental Setup and Algorithms

• The camera is placed in front of the specimen that is put under pressure. The optical axis should be perpendicular to the measuring plane.
• A reference image is recorded.
• An interest operator is used to extract interest points in a region of interest of the reference image.
• A triangle mesh is computed with the Delaunay method
• An image sequence is recorded
• In every image least squares matching is performed to track the interest points from the reference image.
• For each triangle strains and stretch of the triangle area is computed
• A color-coded visualization is computed.

Real-time experiments

An industrial camera was acquired and the algorithm was implemented in C++. Real-time analysis of image sequences were done. A visualization was updated about every second. It could be faster with better processors.

Applying filter methods to reduce noise

The accuracy of the shift measurements of the feature points is limited and causes noise in the visualizations of the strains of the triangles. Spatial and temporal filter methods can reduce these noise effects.

The following filters were applied:

• Empirical orthogonal function (EOF) filtering
• Spatial median filter
• Spatial Gaussian filter
• Spatial moving average filter
• Spatial bilateral filter
• Temporal saw-tooth filter

Combination of the spatial bilateral filter and the temporal saw-tooth filter

© IPF

Related PubliCations

Project partners

• Prof. Dr.-Ing. Steffen Marx, Dipl.-Ing. Gregor Schacht (Institut für Massivbau)
• Prof. Dr. Ing. Gido Bolle (Hochschule Wismar)
• Dipl.-Ing. Oliver Hahn (IBW Weimar)
• Dr. rer.nat. Gerd Kapphahn (Ifem Leipzig)

Contact

• Prof. Dr. habil. Hans-Gerd Maas (project management)
• Dipl.-Ing. Frank Liebold, Dipl-Wirt.-Ing. Robert Koschitzki (project work)