Online fatigue damage assessment for bridges with structural health monitoring system

This paper aims to develop an online assessment approach for evaluating fatigue damage and detection of fatigue critical location of large steel bridges with the long-term structural health monitoring system. The developed approach is on the basis of the real-time data on bridge loading response such as traffic loading, disaster (typhoon, traffic accident, etc) loading data and strain-time histories. Fatigue damage models used in the fatigue crack initiation stage include modified Miner's law and continuous damage model. The Fatigue damage assessment by Miner's law provides a preliminary estimation of fatigue damage and consumed portion of service life in terms of the designed value since the fatigue design uses the Miner's law according the present code. For the element with initiated fatigue cracks, a Fracture mechanics model is used to evaluate fatigue damage and predict residual life for the element in the fatigue crack growth stage. The detection of fatigue critical locations for a bridge section is based on the distribution of the effective stress range for the variable-amplitude spectrum obtained from strain history data measured by str ain gauges on the section. The regular applications, or just after an accident, of the developed approach are expected to provide better understanding on the status of fatigue damage in the deck sections for the bridge under monitoring. In this paper, the application of the developed approach on fatigue damage assessment of the Tsing Ma Bridge is at last demonstrated.