Preliminary investigation of changes in damping mechanism caused by corrosion in reinforced concrete beams.

Abstract

Corrosion induced damages are one of the major durability issues that reinforced and pre-stressed concrete structures face, during their service life span. Vibration - based test methods have gained great attention in the structural health monitoring field during the last decades as, they are non-destructive and easy of conducting, compared to the other test methods. Dynamic characteristics of undamaged and damaged materials vary from each other and reflected through the modal parameters, like natural frequency, damping ratio and mode shapes, etc. In an RC member, along with the initiation of corrosion process, generation and propagation of corrosion products through the voids in concrete, initiate tensile cracks. Further to that, reinforcement will lose its effective diameter and at a later stage, the bond between reinforcement and concrete is reduced. These internal activities can cause changes in the damping mechanism of that member. Finally, failure will occurs due to loss of bearing capacity of the member. This study is focused on the vibration behaviour of reinforced concrete beam specimens, by performing modal tests under free vibration condition. The accelerated corrosion technique is used to induce artificial corrosion at different degrees. The damping ratio, evaluated by half-power bandwidth method and Eigen system Realization Algorithm was used to investigate changes expected in the damping mechanism.