Damage Location in Steel Bridges by Acoustic Emission

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Abstract
This paper explores the use of acoustic emission (AE) for damage location in steel composite bridges. Damage assessment of a steel-concrete composite bridge is obtained using conventional time-of-arrival location techniques in both global and local monitoring trials. The local monitoring aspect of the field investigation is simulated under laboratory conditions and waveforms acquired during both studies are compared. A Finite Element (FE) study of a component of the bridge is presented and compared with location results from the field study confirming regions of possible crack location. Laboratory studies on a 12 m I-beam are presented to explore the use of Lamb waves as an alternative location method to the current time of arrival (TOA) method. The presence and dispersive behaviour of the flexural and extensional Lamb modes in digitised AE signals is observed. The frequency characteristics of the two modes are compared and modal separation via bandpass frequency filtering is demonstrated. This separation is used to estimate the source-to-sensor distance. In addition, the viability of the Lamb wave method for AE source location over extended distances in a real structural component is investigated. Important considerations for the automated implementation of single sensor source location (SSSL) are outlined and a possible extension of the method to provide an insight into the origin of the source is introduced.