ABSTRACT
In recent years, it is believed that pedestrians and vehicular movement cause vibration on pedestrian bridges, which contributes to the structural deformation of the bridge. Hence, there is a need for frequent monitoring using modern-day technology such as fiber optic sensors (FOS) and optical time domain reflectometer (OTDR).
A single-mode and multi-mode fibre cables were connected side by side (SM 10m + MM 0.6m+ SM 10m+ MM 0.6m + SM 10m MM 42m + Pigtail 10.8M) with a total length of 84m using five inclusion boxes and two patch panels, connected end to end. While the OTDR was connected to one of the patch panels using fiber optic patch cable. The connection was placed firmly along the length of the Uniben pedestrian bridge by attaching it to the groove, to measure the frequency of vibration caused by vehicular movement and pedestrians. OTDR was used to obtain snapshots of the stochastic signal, using FOS. Snapshots/Footage of the vehicles was obtained using an Android Phone “TECNO LA7 PRO, Pouvoir 2 Pro, and time settings were properly adjusted for accurate videos and photos. Data and spectra were achieved using OTDR Emulation software (Model: MT9083A-0632), MATLAB 7.3, 2011 Version.
The results from the spectral analysis reveal that the vehicular movement impacts little or no vibration on the bridge as the frequency peak was 0.000Hz and 0.499Hz at a backscatter level of 20.86 dB and -27.68 dB. Conversely, the spectral analysis of the pedestrians showed a dominant frequency peak of 0.476Hz at a backscatter level of 14.53dB. This means that the pedestrians impact a very high frequency of vibration on the Uniben pedestrian bridge.
