Long-term health monitoring of a box-girder bridge

Bridge monitoring system is required to grasp structural deterioration and damage modes accurately. In order to achieve structural health monitoring, it is important to utilize the effective information given from the obtained in-situ data of the acting external disturbance and the responses. This study fully analyzes monitoring data acquired over three years in a box-girder bridge with an orthotropic steel deck, and then clears static changes between temperature and bridge responses, besides examines dynamic responses at the time of earthquake. The data derives a lot of useful engineering information. The bearing responses due to thermal condition remain solid over three years. As for the data during an earthquake, the strain responses and bearing displacement in each part behaves in different phases in the initial stage, after that they gradually synchronize and converge to the condition as observed before the earthquake. By utilizing static data into condition monitoring during the earthquake, it is obviously indicated that residual strain or displacement has not been arisen. The bridge health condition is judged as changeless before and after the earthquake.