Damage detection of a reinforced concrete beam based on fourier spectrum of response to impact excitation

In order to develop damage detection method for a reinforced concrete (RC) structure using an impact hammer excitation, some indices based on Fourier spectrum of a response accelerogram were analyzed. Two test pieces of aRC beam were used: one has sufficient shear reinforcement and the other not. To cause nine stages of damage, a test piece was simply supported and vertical downward forces were loaded. At each damage stage, an impulse excitation was applied and the response acceleration was measured. It was revealed that an index using phase difference spectrum showed fairly good correlation with damage by which bending stiffness was reduced although the index used no information on excitation force. Between the two test pieces, clear difference of the correlation was not observed possibly because bending cracks proceeded for both test pieces.