Issue 46

F. Bazzucchi et alii, Frattura ed Integrità Strutturale, 46 (2018) 400-421; DOI: 10.3221/IGF-ESIS.46.37 406 concrete structure damage scenario, and moreover, the overall external condition appeared healthy (Fig. 9(b)). This unusual structural failure, and the fear of a systematic bias, has been followed by detailed analyses and the structure has been dissected in order to establish the causes. To date, the vulnerabilities of this structure can be summarized as follows:  absence of ductility and structural robustness, there is no redundancy in the prestressing device;  inadequate grout injection inside the cables, which led the water to a preferential way inside the sheathing;  total non-accessibility for structural inspections. Figure 8 : Collapse mechanism. Figure 9 : Prestressing cables in the collapsed joint area (a) ; external concrete conditions (b) . Figure 10 : prestressing cables, extracted and analyzed. It is possible to note the direct correlation between grout content and oxidation rate of both sheathing and strands.