Evaluating the dynamic characteristics of reinforced concrete Beams

ABSTRACT

This experimental study aims to investigate the relationship between the damage and changes in dynamic characteristics of reinforced concrete structures strengthened with Carbon Fiber Reinforced Polymer (CFRP). Modal analysis is a popular non-destructive method for evaluating health of structural systems. A total of eight reinforced concrete beams with similar dimensions are made using concrete with two different compressive strengths and reinforcement ratios. Monotonic loading is applied with four-point-bending setup in order to generate different damage levels in specimens while dynamic testing is conducted to monitor changes in dynamic characteristics of the specimens. In order to study the effect of CFRP on static and dynamic properties of specimens, some of beams are loaded to half of their ultimate load carrying capacity and then are retrofitted using composite laminates with different configuration. Retrofitted specimens demonstrate elevated load carrying capacity, higher flexural stiffness and lower

displacement ductility. By increasing the damage level in specimens, frequencies of beams are decreased, while having strengthened these values, they improve significantly. The intensity of the damage level in each specimen affects the shape of its mode as well. Fixed points and curvatures of mode shapes of beams tend to move toward the location of the damage in each case.