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Giovanni P. Gregori, Giuliano Ventrice,
Sebastiano Pinori, Genesio Alessandrini and
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why dating at the workplace is wrong 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
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.