Structural health monitoring system of railway bridge substructures utilizing soundness diagnosis index correlated with natural frequency

The soundness of structural stability of railway bridge substructures in a river deteriorates over time because the riverbed and overburden can be gradually eroded by river flow. Hence, it is necessary to diagnose the soundness of structural stability of the substructures over time. The soundness can be diagnosed by the size of natural frequency of a primary vibration mode of a pier that was loaded by an impact force. We proposed a new methodology to diagnose the soundness through a structural health monitoring approach. New soundness diagnosis indices based on microtremors and vibrations of piers during train passage were proposed. In order to confirm the applicability of the indices to the soundness diagnosis, a correlation between proposed indices and natural frequencies were investigated through model experiments and in situ measurements. In addition, a long term monitoring of actual railway bridge substructures were carried out using smart wireless sensors that can automatically measure the indices.