Effect of sensors locations and magnitudes of dynamic loads on dynamical properties in structural health monitoring

The monitoring of civil structures and infrastructures are gaining momentum due to the recent technological developments of the various sensors. Typically, almost all structures are vulnerable to dynamic loads which even add more challenges due to the variation of the input excitations amplitudes. Among available alternatives, accelerometers are widely used due to its performance and feasibility in the area of monitoring. After the selection of the sensor, it is a challenge to select and place those sensors in appropriate location (e.g., node must be avoided) to get the meaningful information for the structural health monitoring (SHM). To understand the aforementioned issues, herein, sensors (e.g. accelerometers) are placed on a laboratory setup on a steel bridge of 2m long. And various dynamic type loads have been employed to evaluate their effects experimentally. As for example, the estimated first resonant frequency from all sensors (e.g., locations 01-04) data was found about 5.4Hz under an abrupt impulse type loading condition (for the duration of 36-46 secs in Figure 1). However, the magnitudes in frequency spectrum plot differs quite a lot -46.33, -8.71, -5.79, and -5,01dB, respectively for the sensor locations 01-04. Further, it is observed that the magnitudes of the accelerations vary significantly for different sensor locations (01-04) such as 0.0108, 0.8137, 1.1347, and 1.1472 m/s2. The measured data was recorded with a sampling frequency of 4.80kHz and all the analyses have been performed via MATLAB. The observed behavior shows the critical (e.g. resonant frequencies, damping) dynamical properties of the bridge can be changed significantly due to the magnitudes of the applied excitations. Further, in addition to the magnitudes or variation of the input excitations, the implemented sensors in different location of the bridge shows that the aforementioned critical parameters can also be altered.