An integrated system for structural strengthening and monitoring using CRM composites and FBG sensors

The effective protection of the building stock requires that structural safety is continuously controlled, enabling timely, focused, and cost-efficient maintenance interventions. When dealing with the upgrade of existing structures, smart solutions can be implemented by combining suitable strengthening systems and structural health monitoring (SHM) sensor networks. This work presents a novel integrated technology, in which Fibre Bragg Grating (FBG) sensors are housed in Composite Reinforced Mortar (CRM) composites, made of a pre-cured fibre reinforced polymer mesh and a mortar matrix. The integrated system represents the first attempt to embed self-sensing capabilities into CRM strengthening systems, enabling continuous monitoring of both their integrity and the condition of the CRM-retrofitted structure. CRM-FBG prototypes underwent laboratory development experiments, including direct tensile tests, CRM-to-substrate shear bond tests and pull-out tests. Strains measured by FBG sensors were first validated by comparison against those provided by Digital Image Correlation and then analysed for the early detection of mesh sliding, mortar cracking and shear failure. The proposed CRM-FBG integrated system resulted reliable and showed remarkable potential for combined strengthening and SHM purposes, which contributes to the durable, sustainable, and safe management of the built heritage.