PSI - Issue 78

Arash Rahimi et al. / Procedia Structural Integrity 78 (2026) 1767–1774

1771

Fig. 5. Vehicle automatic stop at the end of the bridge using ultrasonic sensor

Laboratory Testing The first step to identify the modal properties of the scaled-down benchmark railway bridge model was the hammer test. To ensure accurate and reliable modal parameter identification using Covariance-driven Stochastic Subspace Identification (Cov-SSI), a long data acquisition duration was selected. Although in hammer impact testing the transient response typically requires only a few seconds, a longer time record significantly improves the frequency resolution and enhances the stability and clarity of the identified modes. To identify the cases to run we have different possibilities as below. - Number of Vehicles: The data collected under moving single and double vehicles. - Vehicle speed: The base velocity of the bridge would be 7.56 m/s and vehicle maximum speed is about 1 m/s.

Table 2. Vehicle Speed

Vehicle Speed / Base speed

Group Vehicle Speed (m/s)

Description

Slow ( ≤ 5. %)

V1 V2 V3

0.3 0.6 0.9

3.9% 7.9%

Normal (5. % – 8. %)

Fast ( ≥ 8. %)

11.9%

- Vehicle mass: The weight of the bridge deck, Beams and upper supports are 6.28, 2.83 and 5.65 respectively. So, the total weight of the bridge would be 14.76 kg, and the first vehicle is 0.92 and both vehicles are 1.68 kg. as shown below the added mass was performed by using the 5 grams weights.

Table 3. Vehicle Mass

Double Vehicle Mass (kg)

Single Vehicle Mass (kg)

M Single Vehicle / M Bridge

M Double Vehicle / M Bridge

Group

Description

M1 M2 M3

0.92 3.03 4.10

1.68 3.12 4.20

6.2%

11.4%

Light (≤17 %)

20.5% 27.8%

21.13% Medium (17 % – 25 %)

28.4%

Heavy (≥25 %)

For each case the analysis was done at least 2 times and the total number of cases for each set of vehicle speed and mass are 9. Totally 36 cases done for the undamaged condition of the bridge.