PSI - Issue 64

Luigi Petti et al. / Procedia Structural Integrity 64 (2024) 629–636 633 Petti L., Zuchtriegel G., Lupo C., Calvanese V. & De Gaetano C.M. / Structural Integrity Procedia 00 (2019) 000 – 000 5

defects through a competent approach by experts in the field, including engineers, architects, archaeologists and conservators. For an easier and more efficient characterization of decay, the on-site survey uses standardised monitoring forms to identify the reference decay for each element, including wall structures (WS), decorations (D), architraves (A) and horizontal elements (H). The quick assessment considers only the most significant defects with the aim of identifying the most relevant symptoms associated with potential at-risk areas. Figure 3 represents a typical monitoring form, which describes the defects by means of an identification code, and for each of them, the following data is collected: • EXTENSION ( ): describes the extension of the decay with respect to the totality of the element considered. Its value can be 0.2 (little extension), 0.5 (medium extension) and 1 (very extensive); • INTENSITY ( ): describes the intensity of the decay. Its value varies between 0.2 (minimum intensity), 0.5 (medium intensity) and 1 (high intensity); • PHOTO: collection of photos taken to record the specific decay condition; • G: describes the relevance of each decay in the quick assessment of safety conditions. It is variable from 1 (low) to 5 (high) and for each decay is preset; • NOTE: notes and observations. The collected data leads to the evaluation of the following indexes: The Attention Index (AIX) is an absolute parameter and indicates the deterioration of the elements linked to the severity of the type of present decay phenomena determined by the survey of the problems found on site. It considers five thresholds: high (H), medium-high (MH), medium (M), medium-low (ML) and low (L). AIX depends of G, k1. The Relative Decay Index (RDI) classifies the decay phenomena by considering thresholds evaluated by appropriate fragility functions, which relate the damage level to the Relative Decay Values (RDV). In particular, RDV is the sum of the weighted decay phenomena: = ∑( 1 ∙ 2 ∙ ) (1) The fragility functions describe the probability ( ) of exceeding a given level of damage (limit state - ) in relation to the decay intensity, represented by RDV (intensity measure - ) . This condition can be expressed through the following equation, Nielson BG (2005). = [ | = ] (2) The thresholds are therefore initially evaluated on a skilled basis, through a think tank approach. These parameters will need to be updated depending on the evidence identified on-site. Figure 4.a and 4.b show an example of AIX and RDI representation, which is assessed for the case of Insula 4 of Regio VI.

Fig. 3. Example of monitoring sheet.