Distributed fiber optic systems - application to strain measurement of post-tensionedconcrete structures

This article aims to showcase recent advances on Optical Fiber distributed strain measurement systems applied to concrete monitoring. It focuses on their ability to accurately quantify concrete strain in post-tensioned containment buildings of nuclear power plants under various conditions, including instantaneous concrete strain due to pressure tests, delayed concrete strain due to creep/shrinkage, and instantaneous concrete strain due to tendon rupture. To achieve this, the study considers several mockups including the VeRCoRs building, a 1/3 scale post-tensioned concrete containment mockup equipped with a large number of monitoring systems. This mockup facilitates the testing and qualification of distributed measurement systems within concrete structures during both operational phases (for prestressing monitoring) and pressure tests (for measuring instantaneous strain/displacement under pressure). Additionally, a post-tensioned beam was specifically designed and fabricated to examine tendon re-anchorage after cutting. Another objective is to assess various Optical Fiber Cables (OFC) from different suppliers to ensure reliable measurements. The study also aims to test different installation methods, such as embedding the OFC into concrete or attaching them to the external surface using various adhesives.