PSI - Issue 64

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

1261

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Figure 5: Comparison of first three modes of Floßgrabenbrücke between FE simulation (above) and measurement (below).

3.4. Environmental Conditions Example: Influence of Change in Temperature The environmental conditions (e.g., temperature, wind, humidity, etc.) can alter the mechanical properties of a mechanical structure and mask damages or lead to false-positive damage indications. Therefore, they play an important role in the subject of experimental SHM. This is especially true for vibration-based output-only methods because the environmental conditions can contribute to a large or even dominant part to the unknown ambient excitation (e.g., wind). For the bridge structure presented, a significant environmental condition is temperature. This is due to the structural design of the bridge (steel box girder). Therefore, five thermometers monitor the temperature inside and outside the bridge. The influence of temperature changes is illustrated in Table 1 and Figure 6.

Table 1: Exemplary influence of change in temperature (10-minute averaged measurement).

Date

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]

Summer (31 st Aug 2023) Winter (8 th Jan 2024)

17.98 [C°] -4.04 [C°] 22.02 [C°]

1.60 1.68 0.08

1.82 1.90 0.08

2.15 2.25 0.10

2.43 2.55 0.12

2.85 3.00 0.15

3.28 3.47 0.19

∆

∆ [%]

0.050

0.044

0.047

0.049

0.053

0.058