Plastic strains in steel anchorages: axial tension test

The research performed in the laboratory of AGH University of Science and Technology was focused on the analysis of the structural performance of steel ground anchorages. The challenge in this project was to measure not only uniform elastic strains caused by axial tension but also extremely high and unregular strains during yielding. Thanks to DFOS strain sensors, it was possible to analyse this process in a very detailed way, e.g. indicating the areas where yielding starts.

DFOS Sensors Installed: Optical fibre in acrylate coating

Project challenges

How to apply non-invasive diagnostics in demanding historic structures?
How to get precise measurement data to detect local damage and imperfection?
How to measure detailed strain profiles over the entire height of the brick masonry wall?

Benefits of using the DFOS monitoring system

Strain measurements during elastic and plastic behaviour of steel
Detection of the areas (zones) initiating the plastic behaviour (yielding)
Knowledge about residual strains after removing the load
Thousands of measurement points for scientific analysis and design purposes

Results of using the DFOS monitoring system

One of the research goals was to monitor the yielding process of steel anchorages during their axial tension tests. Thanks to distributed fibre optic sensing, it was possible to observe this phenomenon both in length and time domain, creating a 3D plot as shown below. In the initial load steps, uniform distribution of strains was observed over the entire length, but later, after exceeding the value of 2000 µε, the local yield zones were formed and identified by the DFOS-based system.

Technical specifications

3 076 measurement points
2 m of sensing path
2x strain sensors
short-term (load tests)

Example results

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John Doe

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