# Damage Evolution Analysis in a \"Spaghetti\" Bridge Model Using the Acoustic Emission Technique
## 5 Conclusions  
In this work, acoustic emission (AE) data were collected from a load test that was applied to a small-scale spaghetti bridge model, where the load increased until the structure collapsed. Four different parameters (\(b\), \(e\), \(c\), and \(\gamma\)) were computed from the AE data, and their usefulness in identifying damage progression was evaluated. The main conclusions from such a procedure are:  
* The evolution of the coefficients \(b\), \(\epsilon\), and \(c\) through time are suitable measures of the local instability that are associated with changes in the AE regime, with \(c\) (related with the event frequency distribution) being the most sensitive of the three.
* Computing \(\epsilon\) from the RMS-value of the AE signal yields improved sensitivity when compared to the traditional RILEM method.
* Analysis of frequency changes (variations in \(c\) and \(\gamma\) coefficients) are useful not only for considering the isolated AE signals, but also the complete information collected by the AE sensors. In particular, the \(\gamma\) coefficient presented a sharp reduction shortly before the localized damage became evident during the load test, which reinforces this coefficient's usefulness as a failure predictor.
* The minimum values for coefficients \(c\) and \(\gamma\) are consistent with the observations by [PERSON] [6] on the tendency of all phenomenon scales to participate when an instability occurs.
* When compared to the Bundle Model's theoretical predictions, the experimental results presented here highlight the influence of boundary conditions, geometry, and internal organization on the collapse pattern of structures.  
As a continuation of the present research, a Ph.D. thesis is ongoing at the Mechanical Postgraduate Program of Federal University of Rio Grande do Sul (PROMEC/UFRGS). The thesis work will include the study of AE signals from additional bridge models, such as the one used here, as well as other bridge geometries complying with the same contest's guidelines, such as the limits for length and weight.  
Conceptualization, B.N.R.T., I.I. and G.L. ; methodology, B.N.R.T., I.I and G.L.; software, B.N.R.T., T.B.; validation, B.N.R.T.; formal analysis, B.N.R.T., L.A.S.G., I.I.; investigation, B.N.R.T., T.B., M.S.; resources, S.V., G.L.; data curation, L.A.S.G., G.L.; writing--original draft preparation, B.N.R.T., M.S., L.A.S.G., I.I., G.L.; writing--review and editing, B.N.R.T., M.S., I.I., S.V., G.L.; visualization, B.N.R.T.; supervision, G.L., I.S.V.; project administration, I.I. ; funding acquisition, G.L. All authors have read and agreed to the published version of the manuscript.  
This research was funded by CNPq and CAPES (Brazil), and the sponsorship guaranteed with basic research funds provided by Politecnico di Torino and University of Parma (Italy).  
The authors would like to thank the CNPq (Brazilian National Council for Scientific and Technological Development), CAPES (Coordination for the Improvement of Higher Education Personnel) and FAPERGS (Foundation for Research Support of the State of Rio Grande do Sul of Brazil) for their financial aid in this work.  
The authors declare no conflict of interest.