Structural Health Monitoring of a Curved Continuous Steel Box Girder Bridge Under Marine Environment

Abstract

Different from bridges on land, bridges under marine environment are subjected to tide and wave. In order to understand the actual performance of bridge under marine environment, a structural health monitoring system (SHMS) is designed and implemented on a curved continuous steel box girder bridge in the Hangzhou Bay of China. Through the implementation of the SHMS, both environmental parameters and structural response are monitored, including wind, temperature, vibration acceleration, and bearing deformation. By analyzing the monitoring data, characteristics of the environment and structural response are obtained, including the wind field characteristics, the temperature distribution of the steel box girder and the structural dynamic characteristics. From the monitoring results of the girder vibration acceleration, there is an obvious vibration phenomenon found in the lateral direction. Further studies show that the structural vibration has a direct relationship with the tides in the Hangzhou Bay. The obvious vibration is induced by regular ebb and flow, because the lateral modal frequency is as low as about 0.5 Hz which is in the range of the tidal frequencies. Moreover, the foundation scour caused by tide will lower the structural integral stiffness and then the natural frequencies, which may make matters worse. Meanwhile, finite element method is used for structural characteristics analysis and structural response analysis. Comparing the theoretical calculation results and the measured ones, the structural finite element model is verified and modified. And the modified model is used in evaluating and predicting the safety and status of the structure. In the end, some conclusions and management suggestions are given for the bridge under extreme conditions.