Damage Assessment of Corroded Reinforced Concrete Beams Using Modal Testing

Abstract

A laboratory investigation to study the effect of general corrosion on the modal parameters of reinforced concrete beams is conducted in this chapter. Full-scale beams are subjected to reinforcement corrosion until an appreciable amount of steel corrosion damage is introduced using an accelerated technique—namely, galvanostatic method. The states of damage in the test beams are assessed through measurement of crack width, loss of area, and half-cell potential. Modal tests are performed on the test beams after corrosion damage and the modal parameters extracted are compared against that from control beams. The results obtained show changes in the modal parameters especially, natural frequencies and mode shapes. The intensity of the drop in the measured natural frequencies is sensitive to the deterioration state of the beams. Changes in natural frequencies could be established as a damage indicator, which relates to the loss in flexural stiffness of the corroded beams. Using modal assurance techniques to perform orthogonality checks on sets of mode shape from the control and corroded beams, changes can be visualized, which are dependent on the degree of corrosion damage induced. Finally, the load carrying capacity of the beams is determined through static load test and the results are correlated with the state of corrosion damage and changes in the modal parameters. This investigation provides further insights into the use of modal parameters to detect and assess damage in structural concrete elements.