PSI - Issue 78

Marco Gaetani d’Aragona et al. / Procedia Structural Integrity 78 (2026) 968–975

973

and 20% have been considered. In the corresponding analytical model, the strength and the ductility of both the concrete fibers and steel fibers have been reduced. Note that the shear springs are placed at the top of the column bents for two reasons: 1) in general for RC structures it is expected that the shear failure takes place at the top of the column, instead of the foot, due to the lower axial load, 2) in this case the cross section of the pier reduces from the bottom to the top since the column has a prismoid shape, thus shear failure is more probable to occur at the top. Furthermore, considering the deteriorated properties of materials due to corrosion, it results V p <0.7V n thus suggesting pure flexural failure.

3.5E+06

Pure flexure Flexure-Shear

3.0E+06

2.5E+06

2.0E+06

1.5E+06

1.0E+06

Base Shear (N)

5.0E+05

0.0E+00

0.00

0.05

0.10

0.15

0.20

0.25

0.30

Top Displacement (m)

Fig. 3. Pushover curve for the uncorroded multi-column bents considering pure flexural behavior and flexure-shear critical behavior.

In case of bridge piers is more probable that corrosion phenomena only affects the bottom of the column piers that is often underneath and where is more probable the water accumulation. Given this consideration, only the flexural behavior of the column is affected by corrosion. As a consequence, the flexural capacity and thus the shear demand of the column are reduced and V p <0.7V n . Thus the corrosion make the brittle failure transform from flexure-shear critical behavior to pure flexural behavior given the hierarchy of mechanism occurring at the cross-sectional level. Fig. 4 depicts the along with the uncorroded behavior (black line), the corroded lateral response of multicolumn bents in case of 10% (red) and 20% (green) of rebar mass loss. In the uncorroded behavior, a flexure-shear failure occurs, in both the cases of corrosion, a pure flexural behavior is observed for the columns. Conversely, in both corrosion cases, the columns exhibit a purely flexural response, indicating a shift in the collapse mechanism due to the degradation of longitudinal reinforcement. As previously discussed, the lateral flexibility increases as a result of the activation of cap beam shear springs and bar-slip springs, while the shear and axial springs of the column bents remain inactive. In both corrosion scenarios, the initial slope of the pushover response remains unaffected. Although this phenomenon is commonly observed in corroded elements, widely used predictive models fail to capture this reduction (De Domenico et al., 2023; Di Sarno & Pugliese, 2020), as they tend to focus primarily on the post-cracking nonlinear behavior. In case of 10% mass loss corrosion scenario, the peak base shear decreases to 2.9*10 6 N (of about 9%) corresponding to a top displacement of 0.12m (about the same value obtained for flexural uncorroded scenario) after which the peak the capacity slowly reduces, and for Δ top =0.148m a sudden drop due to the progressive concrete crushing rapidly leads the structure to collapse. In this case, despite the flexural behavior, it appears more brittle than the one for the uncorroded structure, and the drop to 80% of maximum base shear occurs for a Δ top =0.15m with a reduction in displacement capacity of 7.4% with respect to the uncorroded flexure-shear critical behavior. For the 20% of mass loss, the peak base shear decreases to 2.6*10 6 N (of 18%) attained for a Δ top =0.104m. Right after the peak, the progressive concrete crushing rapidly degrades the capacity of the bents, reaching collapse for a Δ top =0.116m with a reduction in displacement capacity of 28.4% with respect to the uncorroded flexure-shear critical behavior.