Carbon fiber reinforced polymer(CFRP)has many remarkable merits.It is lightweight and has great rigidity and high intensity. High-durability cable produced from CFRP as reinforcement material is widely used in bridge construction projects.However, there is a dearth of studies regarding damage types and mechanism under fatigue load of CFRP bridge cables.In this paper,we adopt acoustic emission(AE)technology to monitor fatigue damage and failure of the CFRP bridge cables,specifically by monitoring the bridge cable’s fatigue test process and using wavelet transformation to analyze data.Results show that damage on the CFRP cable is divided into three stages.Based on wavelet singularity theory,in each stage of AE,the burst signal is obtained and its time-frequency distribution is achieved through wavelet analysis.According to the analysis results,failure modes in each phase and type of acoustic emission source are easy to determine.The characteristics of waveform,types of damages, and frequency distribution of CFRP bridge cable in different damage phases are collected.Research shows that the method used to determine the types of fatigue damage on the CFRP cable is feasible according to the range of distribution characteristic parameters for acoustic emission signal and type of waveform.
An ultrasonic-guided wave(UGW) is a very promising tool in the field of structural health monitoring and non-destructive test.Numerical analysis was used to simulate the propagation in the rebar and explore the characteristics of UGW in the steel rebar waveguide.Two-dimensional fast Fourier transform was used to process the numerical results and to evaluate the damage.Subsequently,different UGW test influence factors were investigated.The results clearly showed that both the group velocity and the amplitude of longitudinal modes were not very sensitive to stress and temperature variations.However,the received UGW signal energy decreased with the increasing concrete strength.Finally,the interface condition between the concrete and the rebar was investigated.Time-domain and frequency-domain analyses were used to process the received signals.Different interface delamination lengths of the UGW energy attenuation were analyzed and a relationship was obtained.This study successfully proved that UGW is an effective tool in the non-destructive test of reinforced concrete interface delamination.
