Issue 40

M. Mentzini, Frattura ed Integrità Strutturale, 40 (2017) 95-107; DOI: 10.3221/IGF-ESIS.40.09 103 proper combination of bars’ strength and forces lever arm in order to avoid the separation of the drum in two fragments i.e. to ensure the stability of each part. (a) (b) Figure 14 : (a) View of the fracture plane. (b) Inserting the reinforcement on the lower side of the drum. In this picture the drum is upside down. Figure 15 : Inserting the reinforcement on the upper side’s area. The red arrow in the left figure points out the crack’s tips. Drum 11.6 Two areas of the ancient member have severe material losses. The first area, which forms a wedge of 45.50cm height, is on the upper side of the drum (depicted schematically in Fig.16 and symbolized by the letters DF). The second one extends all over the drum’s height and it is symbolized by the letters D 1 F 1 in Fig.16. In addition a crack appears on the upper side, it is symbolized by the letters ΔF 1 in Fig.16, which runs between the aforementioned mass losses, creating a fragment of 34.50cm height (ΔFF 1 top view on the upper side in Fig.16). Finally a severe crack extends allover the height of the drum through the second loss’s surface creating a fault (symbolized by the letters df 2 in Fig.16). The sequence of the actions taken is the following: 1. To restore the drum’s volume two supplements of new marble are created. The join of the supplement “DF” to the ancient remain core was accomplished by inserting titanium bars (to resist tensile and compression forces and subsequently to avoid overturning of the main volume or/and separation from the main volume) from its external surface, after the two volumes came into contact using cement mortar and montage reinforcement (Fig.17). In the next step the main reinforcement (titanium bars) was inserted from outside. In order to achieve the proper anchorage length of the bars, because of the thin thickness of the new volume, the end of the bars has been specially threaded to fit a screw nut through a titanium plate anchor (Fig.18 on the left). 2. The join of the fragment “ΔFF 1 ” to the ancient remain core to avoid separation was accomplished by inserting inclined titanium bars forming 38 0 to the horizontal level, through holes of the drum’s view (created from N. Balanos during the intervention). One of the bars used for the join of the supplement “DF”, contributes to the strength required (Fig.17). 3. To repair the crack “df 2 ” (avoid the separation of the possible resulting fragment from the rest of the drum’s volume, prohibiting its overturning), titanium bars were inserted from the fracture plane of surface “D 1 F 1 ” on the upper side of the drum, while the extension of two of the bars used for the join of the supplement “DF”, contributes to the strength