Structural Ageing of a Cable-Stayed Bridge During Load- Test: The Overall Effect Monitored by Acoustic Emission
Giovanni P. Gregori, Giuliano Ventrice, Sebastiano Pinori, Genesio Alessandrini and Francesco Bianchi
Additional information is available at the end of the chapter
http://dx.doi.org/10.5772/54840
1. Introduction A study is here presented, which was carried out on a steel bridge monitored by acoustic emission (AE), during load-test before its opening to public. Other standard security checks of linear deformation were simultaneously carried out, according to law requirements, by laser monitoring. The focus of the present study is on material fatigue, consequent to load test. This newly constructed viaduct displayed an excellent performance. Hence, it is an effective and suitable reference to be compared with every old metal viaduct. In some respect, and up to some extent, this study also applies to concrete, or brick, or wood bridges. Indeed, fatigue is a permanently ongoing process and, when integrated over time, it affects old structures, causing progressive ageing and loss of performance and security. The difference between bridges constructed by different materials only relies on a different response-time to an applied tress. But fatigue and ageing are a much similar process when dealing with different materials. There is only need for a suitable calibration focused on every given case history. The technique here applied relies on passive AE monitoring in the ultrasound band. AE are spontaneously released by every stressed solid material. Indeed, AE occur as a response to every gentle stress, independent of its cause. It should be pointed out that AE intensity is not of concern for the analysis which is here considered. The only requirement is that an AE signal is detectable. The timing of the AE release, not the intensity, is rather fundamental for the present analysis.
Read All Article .... |