Beat-like behavior of dynamic response deviation of box girder bridges with local stiffness reduction zones: Semi-analytical investigation and numerical simulation

<jats:p>In general, in vibration-based structural health monitoring (SHM) of bridges, natural frequency deviations due to micro-damage are very small and therefore difficult to detect. Through semi-analytical calculations and numerical simulations of the displacement response of a box girder bridge with local stiffness reduction zones, we confirmed that the deviation signal compared to the undamaged response resembles a beat waveform. From this, it can be seen that instead of the frequency deviation, which is difficult to detect in the case of minor damage, detecting the average frequency near the first mode frequency in the displacement deviation signal allows the detection of damage occurrence and evolution from measurement data obtained by a single sensor.</jats:p>