Damage identification of cracked reinforced concrete beams through frequency shift
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The safety evaluation of reinforced concrete (RC) bridges is of the outmost importance, both for the early warning of critical states below a given safety margin and owing to plan maintenance cycles of the infrastructural network. Structural health monitoring based on dynamic testing has become widespread in the last 20 years, leading to very effective operational algorithms able to extract valuable structural features from the recorded signals. However, although in principle it is possible to identify position and severity of the damage by using a finite element model, still some identification issues are unresolved due to the non-linear nature of the oscillations of a cracked beam. In fact, the available experimental data show, for a given damage pattern, a significant underestimation of the natural frequencies given by cracked beam numerical models. This paper presents an approximate solution for the problem of a vibrating damaged RC beam with opening–closing (breathing) cracks. The solution is based on the static equivalence of the kinetic energy and allows incorporating most of the features of a beam loaded above the cracking limit and oscillating under the self-weight with breathing cracks. The comparison with a wide data set collected in the literature points out the predictive capability of the developed analytical formulas. An independent test confirms the theoretical results.
KeywordsRC beam Breathing crack Dynamic test Damage detection Frequency shift
This research has received the financial support from the ERA-NET Infravation 2014 research program through the SHAPE project (Predicting Strength Changes in Bridges from Frequency Data—Safety, Hazard, and Poly-harmonic Evaluation) under Grant 31109806.004. The support of the Infravation program is gratefully acknowledged.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
The Project SHAPE and the research program Infravation completely comply with the ethical standards required by the European Community for research granting. This study does not contain any research done with humans or animals.
Informed consent was obtained from all participants included in the study.
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