An investigation into the acceleration response of a damaged beam-type structure to a moving force

Abstract

Publication information Journal of Sound and Vibration, 332 (13): 3201-3217Publisher Elsevier Item record/more information http://hdl.handle.net/10197/6212 Publisher's statementThis is the author's version of a work that was accepted for publication in Journal of Sound and Vibration. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Journal of Sound and Vibration (VOL 332, ISSUE 13, (2013) that did not appear in the healthy structure is present in the response of the damaged structure. This paper elucidates from first principles how the acceleration response can be assumed to consist of 'static' and 'dynamic' components, and where the beam has experienced a localised loss in stiffness, an additional 'damage' component. The combination of these components establishes how the damage singularity will appear in the total response.For a given damage severity, the amplitude of the 'damage' component will depend on how close the damage location is to the sensor, and its frequency content will increase with higher velocities of the moving force. The latter has implications for damage detection because if the frequency content of the 'damage' component includes bridge and/or vehicle frequencies, it becomes more difficult to identify damage. The paper illustrates how a thorough understanding of the relationship between the 'static' and 'damage' components contributes *Manuscript Click here to download Manuscript: Manuscript RevC.doc Click here to view linked References 2 to establish if damage has occurred and to provide an estimation of its location and severity.The findings are corroborated using accelerations from a planar finite element simulation model where the effects of force velocity and bridge span are examined.

Impact of Road Profile when Detecting a Localised Damage from Bridge Acceleration Response to a Moving Vehicle

“…The consideration of a road profile in a sprung vehicle model renders a significantly rougher mid-span acceleration than found with constant loads. Similar to the approach in [4], the first step toward trying to expose the 'static' and 'damage' components is to use a MAF to remove the main frequency of vibration of the bridge from the signal shown in Fig. 4(b).…”

“…When the vehicle was travelling on a smooth profile [4], once the main bridge frequency was removed, typically all that remained were the 'static' and 'damage' components, but this time, there is a periodic vibration left that obscures any damage features that may be present. If a Fourier transform is carried out on the 'filt 1' signal, the dominant frequency is found to be 1.4 Hz, which corresponds to the bounce frequency of the vehicle.…”

“…They are based on the fact that for some types of bridge damage, the acceleration signal contains a feature that is not present in the acceleration signal of a healthy bridge. In order to visualize the damage feature, Gonzalez and Hester [4] suggest to consider the total displacement response (at a given measurement point) versus time (as the load travels on the bridge) made of 'dynamic' (i.e., derived from the deflection due to the vibration induced by the inertial forces of the bridge), 'static' (i.e., derived from the static deflection of the healthy bridge) and 'damage' (i.e., derived from the extra displacement that occurs at the measuring point due to the damage). These components as illustrated in Fig.…”

“…After exposing the 'damage' component, previous research by the authors shows that it becomes possible to locate and quantify the severity of the damage based on the ratio of the area under the 'damage' component to the area under the 'static' component. However, theoretical investigations in [4] are limited to numerical models of vehicles traversing bridges over smooth road surfaces. The challenges of dealing with acceleration signals generated by a 2-axle vehicle driving on a bridge with a rough profile and subject to noise are addressed in this paper.…”

Isolating the location of scour-induced stiffness loss in bridges using local modal behaviour

“…The model used in this study is similar to the model used in [16,21,32,33] and is intended to be representative of the kind of 2 axle trucks present in modern traffic fleets (i.e. it is not a special test vehicle).…”