PSI - Issue 78

Federica Rauseo et al. / Procedia Structural Integrity 78 (2026) 473–480

479

coupled with differential settlements at the base, may trigger early stiffness degradation or plastic hinge formation even before the lateral load is fully mobilised, as shown by the further capacity reductions in scenarios involving settlements as shown Table 2. Finally, the isolated effect of settlements was evaluated by comparing each configuration with and without the application of differential displacements. On average, the reduction in peak base shear due to settlements alone amounts to 4.9% for the as -built model (AB–ABS) , 10.8% for the CA configuration (CA–CAS) , and 16.3% for the CB configuration (CB–CBS). These values confirm that even moderate settlements can lead to non-negligible performance degradation, especially when interacting with prior corrosion.

(a)

(b)

1000

1000

AB Model A CB Model A CA Model A AB Model B CB Model B CA Model B

AB-PY Model A AB-PY Model B AB-PX Model B AB-PX Model A

900

900

800

800

700

700

600

600

500

500

400

400

300

300

Base Shear (kN)

Base Shear (kN)

200

200

100

100

0

0

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

Displacement [m]

Displacement [m]

Fig. 4. (a) Pushover curves in +X and +Y directions for as-built models (b) Pushover curves in +Y direction for all configurations.

Table 2. Percentage reductions in peak base shear under different scenarios. AB–CA

AB–CB ABS–CAS ABS–CBS

Model A – 10.1% Model B – 8.3%

– 2.0% – 3.2%

– 10.0% – 13.2%

– 12.3% – 16.4%

6. Conclusions This study investigated how pre-existing damage due to reinforcement corrosion and differential soil settlements affects the seismic capacity of an existing reinforced concrete building. Assuming the same structural layout and modelling approach, two fibre-based FE models were developed with different software, allowing for comparison under the same scenarios. Despite the differences between the models, the two numerical approaches yield generally consistent results, particularly in terms of shear peak. The analyses show that corrosion leads to a reduction in peak base shear, especially when uniformly distributed at all column bases. Localised corrosion (CB), limited to the façade columns, has a milder impact. The combination of corrosion and settlements further amplifies damage: this is more evident in the CBS configuration, where the façade columns are corroded along their entire height and the structure is also affected by differential settlements. This condition results in the most severe capacity loss. Overall, analysis results emphasise the need to account for multiple sources of degradation in seismic assessment of ageing buildings. The combined effect of corrosion and settlements can significantly compromise both load and deformation capacities, even when each phenomenon appears limited if considered individually. Future developments of this study could extend this approach to more varied structural layouts and three dimensional models, incorporating additional features such as infill walls, soil typology and building position with respect to the soil settlement profile. This will support the derivation of fragility curves and more comprehensive multi-hazard vulnerability assessments for the existing building stock. Acknowledgements This study was developed within FAIL-SAFE project ("near-real-time perFormance Assessment of exIsting buiLdings Subjected to initAl Failure through multi-scalE simulation and structural health monitoring", Grant No.