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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accumulation of debris and further deterioration of the bridges. All of these observations made during the visual inspection highlighted the need for maintenance and repairs to ensure the structural integrity of the bridges. 3.3. Vibrational Analysis The purpose of the vibration test was to determine the bridge's operating modal characteristics. The placement of the sensors was constrained by the topography and closeness of a watercourse, on the one hand, and the limited access to the track lanes for safety reasons, on the other hand, about concerning reaching the region under the deck. Figure 8 shows the locations of the measurement spots as well as specifics on how the sensors were arranged. The test was carried out using a method that takes into account fixed reference points, as shown in fig. 10, and involved measuring the vertical accelerations at 5 different measuring positions using 5 numbers of triaxial accelerometers, model number G-Link 200. Metallic plates that were bonded to the concrete's surface were used to place the accelerometers on the deck. The G-Link-200 is a wireless 3-axis accelerometer that runs on batteries and has a tough, waterproof casing. The G-Link-200 (fig. 9 (a)) offers exceptionally low noise waveform data that is perfect for applications involving the monitoring of motion, tilt, vibration, and impacts. Predictive maintenance and long-term condition monitoring are also made possible by calculated vibration characteristics. The WSDA®-2000 (fig. 9 (b)), a network-ready gateway for dependable data gathering from Parker wireless and inertial sensors, was used for the data acquisition. The WSDA 2000 has 4GB of onboard memory for data logging in addition to Ethernet, USB 2.0, and J1939 CAN interfaces. The time series were collected with a sampling frequency of 128 Hz during intervals of 10 min. The stochastic subspace identification (SSI) approach was used using MATLAB to identify the bridge's operational natural frequencies.

Fig. 8. Instrumentation of bridges; (a) Measuring the distance between sensors locations; (b) Surface cleaning for gluing the sensor; (c) Preparation of sensor base plate with aerolite; (d) Placing of the sensor on the bridge; (e) Acceleration data recording during the experiment on bridge-3; (f) Acceleration data recording during the experiment on bridge-5.

Fig. 9. (a) Accelerometer sensor (Parker Lord G-Link-200-R); (b) Data acquisition (WSDA-2000).