PSI - Issue 62

Massimiliano Bregolin et al. / Procedia Structural Integrity 62 (2024) 916–923 M. Bregolin et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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hardness (HL). A summarized overview of experimental measurements is presented at some representative points on the footbridge, covering both thickness and hardness parameters in Table 2

Table 2. Thickness and hardness measurements.

Measured thickness (mm)

Tensile strength (MPa) ISO 18265-2013

Structural element

Leeb hardness Vickers hardness Tensile strength (MPa) ASTM E140-07

lower parapet current

5,95

339 437 373 349 352 374 339 437 373 349 352

100 168 120 105 107 121 100 168 120 105 107

340 570 400 360 360 405 340 570 400 360 360

320 539 385 335 341 388 320 539 385 335 341

pillar footplate

14,70 5,75 3,84 4,28 3,28 5,95 5,75 3,84 4,28 14,70

longitudinal current pillar styled diagonal current pillar transverse current transverse current pillars lower current guardrail longitudinal current laid pillar diagonal current pillar transverse current pillar foot plate

To assess the degree of corrosion, the technique of metallographic replicas was used: a hardening resin was applied to the area of interest, creating a copy of the corrosion profile. This copy was then analyzed (Geoconsulting, 2023) and the average maximum depth of corrosion was 1.1 mm, indicating a significant corrosion phenomenon in that area.

Fig. 6. The corrosion profile located at a significant point at the anchoring of the rope.

5. FEM model of the footbridge The footbridge was modeled using the Midas Gen software, as illustrated in Fig. 7a. All components of the deck and stringers were simplified as beams, while hangers and cables were represented as trusses. A fixed constraint was applied at the base of the stringers, and hinges were introduced at the ends of the deck and cables. The material chosen was S235 structural steel. The model's validation occurred through comparison with experimental results: the mid- span deflection resulting from a load of 3.1 kN/m² closely matched the experimental value of 43.5 mm obtained during the load test. The modeling process involves some simplifications. From the comprehensive modal analysis, the modes affecting the deck deformability were extracted and graphically presented in Fig. 7 and numerically in Table 3. X and Y axes are in the horizontal plane, with the X-axis parallel to the longitudinal axis of the footbridge; the Z-axis represents the vertical direction. The FEM numerical model should be calibrated based on experimental measurements (Model Updating). In our case, the study aimed to verify a satisfactory agreement between the FEM model and previous experimental results.