Vibration-based detection of small-scale damage on a bridge deck

Vibration-based damage detection (VBDD) methods use damage-induced changes to the dynamic properties of a structure to detect, locate, and sometimes quantify the extent of damage. This paper describes a laboratory-based experimental and finite element analysis study conducted to evaluate the ability of five different VBDD methods to detect and localize low levels of damage on the deck slab of a two-girder, simply supported bridge, with a focus on using a small number of sensors and only the fundamental mode of vibration. It is demonstrated that damage can be detected and localized longitudinally within a distance equivalent to the spacing between measurement points using data for only the fundamental mode shape before and after damage, defined by as few as five evenly spaced measurement points. The localization resolution declines by approximately 50% near supports. Increasing the number of measurement points improves the localization resolution of the techniques, although not always in proportion to the resulting decrease in measurement point spacing. Incorporating data from two additional modes was not found to significantly improve the localization performance.