Abstract
In bridge structures worldwide, carbon fiber-reinforced polymer (CFRP) sheets are applied to strengthen weak components, especially concrete girders that are at a high risk of rapid degradation during the bridge’s operation owing to impacts from the superstructure’s weight and traffic loads. Regarding the thermography-based method (TM), although deteriorations in the concrete core are some of the main defects in concrete structures strengthened with CFRP, these do not receive as much attention as damage in the CFRP. Therefore, the interpretation of the structural health in terms of these defects using TM is still unclear. The problem presented in this work addresses the quantification of delamination inside the concrete part of a specimen with a CFRP sheet installed on the surface (assumed to be the girder surface strengthened with CFRP) via step heating thermography. Additionally, the empirical thermal diffusivity of concrete girders strengthened with a CFRP sheet (CSC girder), has not been provided previously, is proposed in the present study to predict delamination depths used for field investigations. Moreover, the effect of the CFRP sheet installed on the structure’s surface on the absolute contrast of delamination is clarified. Finally, advanced post-processing algorithms, i.e., thermal signal reconstruction and pulsed phase thermography, are applied to images obtained with step heating thermography to enhance the visibility of delamination in CSC girders.
Highlights
The aging of structural components is one of the most critical factors leading to the deterioration of concrete bridges [1]
Advanced post-processing algorithms, i.e., thermal signal reconstruction and pulsed phase thermography, are applied to images obtained with step heating thermography to enhance the visibility of delamination in concrete strengthened with CFRP (CSC) girders
An effort was made to detect delaminations at the core of a specimen assumed to be the surface of a concrete girder strengthened with one carbon fiber-reinforced polymer (CFRP) layer not exposed directly to the sunlight using a thermography-based method, i.e., step heating thermography
Summary
The aging of structural components is one of the most critical factors leading to the deterioration of concrete bridges [1]. In Korea, the proportion of bridges over 30 years old was 30.9% in 2015 and this value will increase to 70.2% by 2025 [2]. Of bridges were over 50 years old by 2013 and this number will increase to 43% in 2023 and 67% in. Defects in the concrete structures in the forms of cracks, delamination, and spalls are unavoidable and mainly caused by rebar corrosion [4,5]. The worldwide cost for the maintenance and repair of concrete structures affected by the corrosion amounts to millions of dollars each year, as reported by
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