Using the vibration envelope as a damage-sensitive feature in composite beam structures

A novel approach of damage detection in composite steel-concrete composite beams is suggested. Based on the idea of using the envelope's profile deflections and rotations induced by a moving load, this approach can lead to a practical cost-effective alternative to the traditional use of accelerometers and laser vibrometers.A parametric study has been undertaken, quantifying the sensitivity of the dynamic response of a realistic composite bridge to the presence of damage at different levels of partial steel-concrete interaction and velocity of the moving load.When compared to shifts in the natural frequencies, it has been verified that the proposed approach generally enjoys a higher sensitivity (so damage can be detected at an early stage), is more effective when closer to the ends of the bridge (where shear studs are more likely to be damaged), and displays an ordered set of results (which would reduce the possibility of a false damage).Further work is required to assess the effects of uncertainties and the adoption of more refined models for the moving load.