Abstract

Structural Health Monitoring (SHM) techniques are often used for detecting damage and diagnosing the structural conditions. Fibre Optic Sensors (FOS) are found to be very accurate and durable for outdoor applications including embedment in reinforced concrete structures. However, there are many issues related to installation and constructability of SHM systems and in-situ installation of FOS on rebars in reinforced concrete (RC) elements, especially when Fibre Reinforced Polymer (FRP) bars are used as reinforcements.

Here, a solution is provided for installation of a FOS strain sensor by mounting it on a supplementary bar a priori and then attaching it to the main reinforcing bar of interest at the construction site prior to concrete pouring. Such innovative deployment system for FOS is particularly advantageous for developing a practical SHM system for infrastructure. However, the performance of such systems under various loading and climatic conditions is not very well known. The objective of this research is to assess the performance of the said system used in concrete beams reinforced with FRP bars, under normal and adverse environmental conditions.

A set of twelve specimens with and without exposure to various environmental conditions have been tested under static and fatigue loads to determine the effectiveness of the sensing system in these conditions. Apart from measuring the response quantities like strain and deformation, the Scanning Electron Microscopy (SEM) technique has been used to determine the effect of the adverse environmental conditions on the rebars. In addition, numerical modeling of the beams using the Finite Element Method (FEM) has been applied to carry out a parametric study on the effect of the properties of concrete and the bar sizes on the performance of the above sensing system.

From the present study, it is observed that the proposed system works well in terms of capturing the strain under static and fatigue conditions in normal and adverse environmental conditions. However, the performance of the sensing system degrades in the case of alkaline immersion. The outdoor or wet and dry conditions do not affect the performance of the system.