n Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese - Dynamic behaviour of damaged reinforced concrete beams and application of white noise analysis to crack detection

Volume 51, Issue 2
  • ISSN : 1021-2019



Vibration monitoring is a useful and precise method for non-destructive evaluation of defective members. The fundamental concept underlying this method is that the dynamic properties and responses of the structure will change if any defect occurs. The aim of this paper is to investigate the responses of damaged reinforced concrete members to dynamic excitation and to identify the location of probable defects. A powerful multi-purpose finite element (FE) package, COSMOS/M, is used for the analysis of the damaged concrete cantilever beams studied in this paper. The mechanical and geometrical properties of all beams are the same, but the location and the depth of the cracks are changed in these members. The analysis process is performed in the frequency domain. Initially, a modal analysis is performed to determine and compare the natural frequencies and mode shapes of the various defective members. Each member is then excited by an individual vertical force, with the specifications of white noise located at the end of the member, and the responses are monitored at different locations along the member. These responses are used to investigate the dynamic properties of the defective members and to identify the crack location.

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