Issue 47

M. Marchelli et alii, Frattura ed Integrità Strutturale, 47 (2019) 437-450; DOI: 10.3221/IGF-ESIS.47.34 448 Component Case A (maximum 90) Case B (maximum 105) Case C (maximum 105) Wire mesh 12 (A2) 11 (A1) 2 (A0) Top rope 15 (A2) 3 (A0) 0 (A0) Bottom rope 10 (A1) 4 (A0) 0 (A0) Intermediate ropes 0* (A0) Support ropes 4 (A0) 0 (A0) Connection between mesh panels 0 (A0) 5 (A1) 0 (A0) Mesh-top rope connection 0 (A0) 5 (A1) 0 (A0) Mesh-bottom rope connection 0 (A0) 0 (A0) 0 (A0) Mesh-intermediate rope connection 0* (A0) Global score 52% 30% 1% Table 7 : Results of the survey campaign on the three cases commented in the text. The sum of the scores and the most severe maintenance level (in round brackets) are reported for each component. If the component is not present, a sign * is added to the score. C ONCLUSIONS AND FURTHER OUTLOOKS rapery net systems are widely employed and profitable measures to mitigate the risk of rockfall events. Nevertheless, their failure or destruction would cause serious consequences, both in term of causalities and economical damages. Due to their importance, a continuous monitoring would be profitable to evaluate the maintenance of their efficiency despite ongoing ageing and/or local damages. Unfortunately, continuous or periodic monitoring is rarely adopted, as it is high time-consuming, and thus no quantitative data are available for the planning of the maintenance works. As a consequence, the proposed quick-assessment procedure herein reported aims at addressing the problem of estimating the efficiency of a rockfall drapery mesh system and establishing a priority list for intervention works. The presented method is based on a multi-criteria analysis, involving an encoded screening survey. The leading idea is that either the deterioration of several minor elements or the damage of a unique fundamental element of a drapery system can compromise the whole system efficiency. This entails a double hierarchy problem, since the final evaluation depends both on the damaged/deteriorated part and on the magnitude of the damage itself. The process is implemented through a list of observed items that the surveyor must check in analysing the protection structure. A damage level and a class of importance for each entry let to assign a global score and a maintenance level to the structure, indicating if urgent reparation works are needed. The lack in the prescriptions for such kind of hazard mitigation structures lead the authors in fixing the attention on two different drapery types. Similarly, the procedure can be implemented on other installation types, keeping fixed the identification of the main components and the effects of damage on the overall behaviour. A site campaign was performed to validate the weights assigned to each issue, despite the valuable range of observed different solutions, indeed, a good agreement between the observed conditions of the system and the obtained results emerges. The double information obtained by the global score and the global maintenance level provided a compelling solution to understand both the severity and the extension of the possible required maintenance intervention. Further developments can be achieved, expanding the methodology for other mitigation measures [27]. A CKNOWLEDGEMENTS his work has been supported by Regione Autonoma Valle d’Aosta under the framework of RED - Risk Evaluation Dashboard project. D T