Measurements of extremely wide cracks in prestressed concrete beams

Prestressed concrete beams, equipped with EpsilonSensors, were investigated during prestressing and mechanical load tests. Twelve beams were made to provide statistical confidence about the obtained results. One EpsilonSensor was arranged in such a way to create four measurement sections at different beam heights. Thanks to that approach, it was possible to detect cracks and calculate their widths, but also to assess the crack
depths depending on the load step.

DFOS Sensors Installed: EpsilonSensor

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

Full knowledge on crack morphology during entire research (all load steps)
No risk of sensor breakage during the extreme crack-induced strains
Calculation of crack widths, but also identification of their depths inside the beam
Reliable scientific data on structural performance

Results of using the DFOS monitoring system

EpsilonSensors embedded inside concrete allowed us to assess the effectiveness of prestressing process. However, the critical research stage were mechanical bending tests, where the knowledge on crack morphology was of key importance. EpsilonSensors provided spectacular results, measuring extensive cracks (> 2 mm) with crack-induced strains exceeding 2.7% (27 100 με). Such values were not previously described in the literature. Our sensors provided reliable data for scientific analysis.

Technical specifications

60 000 measurement points
300 m of sensing path
12 x EpsilonSensor
short-term (laboratory)

Example results

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