PSI - Issue 64

Pavel Ryjáček et al. / Procedia Structural Integrity 64 (2024) 228 – 237 Pavel Ryjacek / Structural Integrity Procedia 00 (2019) 000 – 000

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is clear that this defect is practically not shown in the natural frequencies. The failure of a large part of the prestressing ropes led to an overall softening of the structure and therefore to a reduction of the natural frequencies, but less than the measurement uncertainty. Furthermore, it can be seen that this type of defect does not affect the eigenmodes in a detectable way. The effect of the absence of grouting in the main span and the corrosion of the prestressing cables (Beta) was only reflected in an increase in the flexibility of the structure as a whole, see Fig. 12.

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b

Fig. 12 Change in the curvature of the 7th CAMOSUC(j),x mode shapes from corrosion of Beta cables, for (a) 86 and (b) 24 sections

11. Combined effect of corrosion of prestressing (Beta) and supporting cables (Alfa) For detection by advanced methods, the eigenmodes of the reference undamaged model are shown compared with the eigenmodes from a model in which a combination of simultaneous failure of the main supporting cables, absence of grouting of the prestressing cables and significant corrosion loss of the prestressing cables was used. For the model with 86 sections, all three methods can be used to locate the failure in the vicinity of section 39. The distribution of the increase in flexibility of the structure becomes irregular in the vicinity of section 39, the absolute value of the second derivative of the change in the diag. members of the matrix [  ] increases in the vicinity of section 39, see Fig. 13, and the CAMOSUC(j),x. values for the 4th, 8th, and 10th natural modes also show a local increase here, see Fig. 14. On the other hand, for the model with 24 sections, this defect cannot be localized.

a b Fig. 13 Second derivative of the change in the diag. members of the modal flexibility matrix [  ] for the cables Alfa and Beta corrosion, for 86 (a) and 24 (b) sections

a b Fig. 14 Change in the curvature of the 4th CAMOSUC(j),x mode shapes from corrosion of Alfa and Beta cables, for (a) 86 and (b) 24 sections