The use of changes in vibration propelties for damage detection of civil infrastructure has been a subject of investigation for many years. However, the implementation of vibration-based techniques in reinforced concrete structures is extremely limited, due principally to the absence of suitable crack models. The aim of this research is to determine whether a flexural crack model incorporating non-linearity is able to quantitatively reproduce changes in vibration characteristics of cracked reinforced concrete beams, and to assess the sensitivity of changes in vibration properties to realistic damage scenarios. To better understand cracking mechanisms in concrete, experiments on un-notched plain concrete prisms under monotonic and cyclic four-point bending were conducted. The fracture process in the prisms was captured using a digital image correlation system. In addition, a numerical model of a plain concrete prism based on the fictitious crack approach is developed. The model adopts cyclic constitutive laws and is validated against the experimental results. To examine its suitability for vibration-based damage detection, the fictitious crack approach is used to develop a reinforced concrete beam model subject to incremental static four-point bending. The dynamic behaviour of the model, such as changes in resonant frequency, modal stiffness and level of non-linearity, is examined using different sinusoidal excitations. The beam model is validated against experimental results of beams under incremental static loading. Another set of experiments on beams under cyclic loading was carried out to assess realistically the sensitivity of changes in vibration characteristics. The results revealed that the crack model quantitatively predicts changes in vibration characteristics and that the sensitivity of these changes is influenced by the condition of SUPPOltS. The trend of changes in the level of non-linearity follows a softening behaviour and thus it may not be suitable for damage detection applications. The experimental results of the beams under cyclic loading give rise to the question of the suitability of vibration-based techniques for damage detection.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:604573 |
| Date | January 2012 |
| Creators | Hamad, Waleed Ibrahim |
| Publisher | University of Nottingham |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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