This paper presents a methodology for the use of vibration monitoring as a tool to assess the damage of reinforced concrete beams strengthened by CFRP sheets. The method is based on the experimental flexibility matrices of reinforced concrete beam specimens. The specimens were gradually damaged and the changes of modal parameters were measured from the initial to the failure state. The noises were removed from the experimental data and the flexibility matrices were estimated by the three lower frequency modes of the beam specimens. The results show that the changes of flexibility matrices can successfully detect the damage by using a limited number of vibration modes. The method can also shows the effect of increasing bending stiffness of reinforced concrete beams after applying the CFRP sheets.

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