PSI - Issue 52

Govardhan Polepally et al. / Procedia Structural Integrity 52 (2024) 487–505 Govardhan Polepally/ Structural Integrity Procedia 00 (2019) 000 – 000

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4.3. Operational Modal Analysis (OMA) In this study, an SSI analysis was conducted to estimate the dynamic properties of bridges undergoing ambient vibration testing (AVT). To achieve this, a train was deliberately passed over the bridge at its maximum speed of 10 kmph, and data was recorded during this process. The recorded data was then used to identify the model parameters, which are listed in Table 12. These parameters play a crucial role in characterizing the behavior of the bridge under dynamic loading conditions. The same has been carried out remaining bridges.

Table 12: Operational modal analysis results. Frequencies (Hz) bridge1

bridge2

bridge3

bridge4

bridge5

Mode 1 Mode 2 Mode 3 Mode 4 Mode 5 Mode 6 Mode 7 Mode 8 Mode 9 Mode 10 Mode 11 Mode 12 Mode 13 Mode 14 Mode 15 Mode 16 Mode 17 Mode 18 Mode 19 Mode 20

18.023 24.228 24.852 29.841 32.327 34.646 36.105 37.339 38.509 39.509 42.939 45.290 46.701 50.472 51.266 52.322 52.583 56.155 60.751 60.916

27.680 29.851 33.492 34.175 36.309 37.232 38.073 39.651 42.016 43.496 45.085 46.169 47.771 50.440 51.022 53.218 55.520 57.557 60.397 63.738

22.759 24.003 25.507 27.851 30.113 33.124 35.285 37.225 39.010 41.892 44.043 45.265 46.891 49.797 52.793 53.657 55.436 55.906 58.379 60.365

18.700 20.149 22.663 26.594 29.427 32.464 33.289 36.850 39.447 39.874 44.123 45.893 48.819 50.279 51.888 53.583 54.678 56.398 57.585 64.002

21.115 24.651 25.270 30.273 31.987 36.329 39.053 41.056 44.796 47.064 50.029 51.107 52.687 55.359 57.428 57.615 59.129 60.341 60.711 64.009

Table 13 in this study presents the differences between numerical and experimental analyses. These differences reflect the variations in frequencies obtained from the two methods. A positive difference indicates that the experimental analysis yielded higher frequencies compared to the numerical analysis, while a negative difference suggests lower frequencies. The numerical analysis provides predicted frequencies for each mode of vibration, whereas the experimental analysis provides the actual frequencies obtained from physical testing. By comparing the results, it becomes possible to observe the differences between the numerical and experimental analyses. The interpretation of these differences can provide insights into the accuracy of the numerical model used for analysis. When the numerical and experimental results closely match, it suggests that the numerical model is reliable in predicting the dynamic behavior of the bridges. However, significant differences between the two sets of results may indicate the presence of uncertainties, modelling errors, or variations in the physical properties of the bridges. These differences serve as indicators for further investigation and refinement of the numerical model if necessary.