Experimental study on fatigue damage of continuous steel–concrete composite beam by acoustic emission

Abstract

To investigate the developing process and mechanism of internal fatigue damage of continuous steel–concrete composite (CSCC) beams, the fatigue test of two-span CSCC beams under cyclic loading was conducted, and the acoustic emission (AE) testing method was used to monitor the fatigue damage accumulation during loading. Internal AE propagation characteristics and residual deflection were compared to analyze the overall damage process as well as the boundary points of each fatigue stage. The fatigue failure mechanism of CSCC beams was deduced from an internal damage point of view. The fuzzy C-means algorithm was used to cluster the AE signals and extract the signals of the concrete structure. According to the energy accumulation-release signal of the fatigue crack tip, a novel method for fatigue damage location identification of the concrete structure was proposed, and the propagation characteristics of the fatigue crack along with the variation law of the AE wave velocity within the concrete slab were further investigated. Control parameters for fatigue damage, similar to the relationship between magnitude and frequency of earthquakes, were calculated, and the warning signs of fatigue failure of CSCC beams were inferred. The AE cumulative energy-based fatigue damage model was proposed to predict the damage status and fatigue life of the composite beam. Results have shown that the AE detection method is capable of continuously and accurately monitoring the fatigue damage within the composite beams in real-time as opposed to inspections that are solely based on appearance. The fatigue damage energy model also confirmed the fact that the fatigue damage growth follows an exponential function. The fatigue damage energy model and the AE method proposed based on AE attributes provided a more feasible and stringent method for fatigue damage prediction and analysis for CSCC beams.