PSI - Issue 44

Ubaldo Saracco et al. / Procedia Structural Integrity 44 (2023) 721–728 Ubaldo Saracco et al./ Structural Integrity Procedia 00 (2022) 000–000

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4.6. Scenario 4: Corroded vertical members This scenario shows that the corroded vertical elements do not particularly affect the bearing capacity of the structure, which sees a λ max almost comparable to that of the intact model. The elasto-plastic state of the structure shows that the lower chord is still the only responsible of the collapse. The vertical members are largely in the elastic range, except for a small portion of the wings. The overall displacement of the structure up to failure is 400 mm. Analysis results of this scenario are shown in Figure 8.

a

b

c

λ max = 1.598 > 1

Fig. 8. (a) Push-down curve; (b) elastic-plastic deformation state of the bridge; (c) elastic-plastic state in vertical member.

4.7. Comparison among results All the push-down curves of the five scenarios considered were plotted and compared to each other in Figure 9. From analysis results it appears that only scenario 1 with corroded deck elements and scenario 4 with corroded vertical members exhibit λ max > 1. To stay on the safe side, this load multiplier was measured before the first collapse phenomena although, following large displacements, hardening phenomena could be generated to increase this value. Moreover, scenarios 1 and 4 are those attaining the greatest displacement until collapse.

Fig. 9. Comparison of push-down curves.

5. Dynamic linear analysis Analyses were also conducted to evaluate the vibration modes of both the intact structure and the four corrosion scenarios. The periods (T) and the masses (M) in longitudinal (X), vertical (Y) and transverse (Z) directions were identified and maximum and minimum values are in bold in Table 1. It can be seen how there is no significant difference either in the participating masses or in the periods. The major differences are between scenario 0 and scenario 2, where along the axes X and Z there is a difference of about 5.5% and 3.5%, respectively, in terms of both