Damage localization using low-frequency bridge acceleration component under a moving vehicle

Monitoring the health of short-span and medium-span bridges in urban transportation systems is a crucially important issue in civil engineering, as is locating damage. Earlier studies have attempted to use bridge deflection or acceleration to locate damage. However, the deflection is not so sensitive to enable damage location. Few studies have investigated low-frequency acceleration responses. For this study, a proposed modelfree method is evaluated for damage localization using low-frequency bridge acceleration under a moving vehicle. First, the bridge dynamic responses in a vehicle-bridge interaction (VBI) system are derived theoretically, where the bridge is modeled as a simply supported beam, the vehicle as a moving sprung mass, and damage as a reduction of the beam's bending stiffness. A partially moving loading model is proposed to explain the influence of the structural damage on the dynamic behavior of the beam. A simple relation was found between low-frequency bridge acceleration and the damage location. Specifically, an abnormal "bump" occurred on the low-frequency bridge acceleration when a vehicle passes over the damaged area. Using this relation, one can directly locate potential damage from the low-pass filtered acceleration time history of the beam. A series of numerical analyses and laboratory and field experiments were conducted to validate the proposed damage localization method.