<p>During the examination of data obtained from scanning an operational steel girder bridge, local ripples were noted in horizontal elements that were expected to be planar in nature (such as girder flanges). It was hypothesized that these ripples are a result of the bridge vibrating under truck traffic. The objective of this paper is to examine this hypothesis through the use of data obtained from an operating highway bridge together with the use of numerical and physical models. After analyzing the data, by estimating the distance between the peak of these ripples (and translating this into time using the data acquisition metrics) the frequency of the vibrating object can be estimated. For the operating bridge and physical model employed in this research, the natural frequencies were estimated within 2% to 10% and 0,22% to 5%, respectively.</p>
