PSI - Issue 44

Romina Sisti et al. / Procedia Structural Integrity 44 (2023) 1848–1855 Romina Sisti et al./ Structural Integrity Procedia 00 (2022) 000–000

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9. Vaults Vaults were not a macro-element specifically analyzed, but some important observations were made. In particular, the main identified problem is the different interpretation of the structural or non-structural function of this elements. Neither in the manual nor in the A-DC form is it explicitly specified if the mechanisms relating to the vaults of the various macro-elements should be considered even when the vaults are non-structural. The choice is in fact left to the compilers and thus becomes entirely discretionary, causing low reliability of the data relating to these macro-elements. A possible solution could be to include in the form in each of the mechanisms relating to vaults the possibility of tracking if the vaults are structural, non-structural or if this information cannot be identified. Keeping the information on the nature of the vaults (structural or non-structural) separate would be very useful from the point of view of a complete understanding of the structural behavior of the church. 10. Dome The inconsistencies registered for the macro-element dome are around 50%, with the higher level of ambiguities (29%). This is mainly due to the fact that in several churches, axial-symmetrical vaults or domes are present in correspondence of the altar (Fig. 7a) Often, even when there are segmental and unimportant domes/vaults, some compilers describe the element through the M14 mechanism (related to the dome) while others through the M18 mechanism (vaults of the presbytery/apse). In general, the analysis showed that the possible configuration of this type of element are many, and it is difficult to establish an unambiguous criterion for defining the presence of the dome element. It is considered that the recognizability from the outside of the dome determines a structural discontinuity with respect to the nave and therefore in these cases it is more correct to identify a separate element through the M14 mechanism. It should also be emphasized that the M14 mechanism refers to damage types specific to domes, and such damage is not easily distinguishable in structures whose configuration is considered "intermediate" between that of a dome and of a vault. In addition, as for the vaults, it is necessary to define whether domes are structural or non-structural. When the dome is non structural, the element must be described as a presbytery/transect/apse vault. 11. Adjoining structures The interaction of the church with adjacent structures is considered through the M25 mechanism, however its definition is clearly neither in the A-DC form nor in the instruction manual. In the A-DC form the mechanism is defined as “interactions near plano-altimetric irregularities (adjacent structures, flying buttresses)”. The explanatory drawings attached to the form indicate more generically "interactions near irregularities". A first uncertainty is related to what type of plano-altimetric irregularities must be considered: some technicians consider only those generated by adjacent structures to the church, others also consider those between the portions of the church itself (chapels, apses, bell towers). However, the latter approach is considered incorrect as the interactions between the macro-elements that compose the church (nave-chapels-apse-bell tower) are already described through the other mechanisms and therefore considering them again through the M25 mechanism would lead to an overestimation of the damage. A second uncertainty concerns the structural irregularities resulting from different construction phases. Since the inspection of the church is carried out in an emergency phase, the technicians' knowledge of the historical evolution of the building will almost always be scarce and for this reason, the correct identification of structural discontinuities can be complicated or approximate. Including them in the M25 mechanism would lead to uncertainties that could compromise the homogeneity and reliability of the data collected. 12. Standing-out elements and bell gables The A-DC form describes the behavior of all standing-out elements in a church through the same mechanism (M26), without giving the possibility to systematically specify which type of element is referred to. Among the standing-out elements one of the most common, especially in small churches, is the bell gable. In some cases, it may not be easy to identify this element because of its poorly visible position. Furthermore, when the bell gable rest on structures adjacent to the church (Fig. 7b), with the same or different ownership, the choice of whether or not to consider the element in the A-DC form is not always univocal. The A-DC form requires the assessment of damage in the bell gable through the M26 mechanism, listing the term “bell gable” in its description; however, some technicians consider the bell gable through the M28 mechanism. This mistake could be induced by the user manual of the A-DC form, where a bell gable appears among the examples of the M28 mechanism, therefore it might be cleared in the manual that the bell gable should be considered as M26. Interpretive differences between the technicians were observed in hybrid situations between bell-gable (composed of a single wall) and bell tower (composed of at least 4 walls), as in Fig. 7c. In these cases, it is not possible to provide a valid general interpretation, each technician will have to carefully evaluate the geometric-structural details of the specific situation and decide whether it is more appropriate to interpret the element as a bell gable or as a real bell tower