PSI - Issue 64

Maximilian Rohrer et al. / Procedia Structural Integrity 64 (2024) 1256–1263 Rohrer, Moeller, Lenzen / Structural Integrity Procedia 00 (2019) 000 – 000

1262

7

Figure 6: Exemplary recorded spectrum of change in temperature (10-minute averaged measurement).

3.5. Operational Conditions Example: Influence of Traffic Operational conditions are, much like the environmental conditions, a crucial part of SHM. They characterize influences which are due to the operation of a structure (e.g., rotation of rotor blades for wind turbines, traffic for bridges, etc.). To demonstrate the influence of traffic on the experimental structure, two 10-minute averaged acceleration measurements taken in winter at a sampling frequency of 10,000 Hz are compared in Table 2 and Figure 7. The difference in peak heights but not in frequency indicate that the traffic influences the average power of the system but not the measured frequencies. This is because the additional mass is not static. The average time to cross the bridge is about 17 seconds. With multiple vehicles crossing the bridge from both directions during the 10-min measurement time, the influences of the additional masses are averaged out.

Table 2: Influence of traffic on identified eigenfrequencies (10-minute averaged measurement).

Average Temperature

1 st EF [Hz]

2 nd EF [Hz]

3 rd EF [Hz]

4 th EF [Hz]

5 th EF [Hz]

6 th EF [Hz]

Normal traffic

-4.78 [C°] -4.90 [C°] 0.12 [C°]

1.68 1.68 0.00

1.91 1.91 0.00

2.27 2.27 0.00

2.58 2.62 0.04

3.00 3.00 0.00

3.48 3.48 0.00

No traffic

∆

Figure 7: Exemplary spectrum comparing the influence of traffic (black, left ordinate) and no traffic (red, right ordinate) (10-minute averaged measurement).