Sewer concrete collector refurbishment: strains, cracks and displacement measurements

The concrete sewage collector was constructed in 1964 and is now reinforced with Glass-fiber Reinforcement Plastic (GRP) panels. EpsilonRebars (ER) and the EpsilonSensor (ES) from the Nerve- Sensors family were installed inside the near-to- surface grooves to verify the strengthening process. ERs were placed longitudinally over the entire 150 m long section, while ES was installed in selected key circumferences. The system allowed for detailed analysis of strains, cracks, displacements and temperatures.

DFOS Sensors Installed: EpsilonRebar

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

Detection of all the cracks between the old segments (with width estimation)
Calculation of vertical displacement profiles (settlements) along the length
Full deformation control during strengthening process (injection + FRP panels)
Reliable monitoring system working in extremely difficult external conditions

Results of using the DFOS monitoring system

Nerve-Sensors allowed for direct measurements of strains and temperatures, as well as detection of extremely small cracks, including their width change estimation. Moreover, thanks to the appropriate sensors’ arrangement, it was possible to calculate vertical displacements caused by the dead weight of GRP panels and mortar injection applied during strengthening. Example crack morphology along the safety critical section as well as vertical displacement profile over entire length are presented in the figures below.

Technical specifications

51 000 measurement points
510 m of sensing path
3 x EpsilonRebar, 1 x ES
construction (strengthening)

Example results

Recomendations (optional)

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John Doe

Project partner

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