FATIGUE LIFE PREDICTION FOR ORTHOTROPIC STEEL DECK DETAILS WITH A NONLINEAR ACCUMULATIVE DAMAGE MODEL UNDER PAVEMENT TEMPERATURE AND TRAFFIC LOADING

Abstract Taking into account uncertainties in the nonlinear process of fatigue damage accumulation for the fatigue life prediction of the structural details in orthotropic steel decks, a novel fatigue damage regression analysis model and a new fatigue reliability assessment method based on the nonlinear fatigue model are developed and then used with reliability profiles to predict the fatigue life of details in the orthotropic steel deck. In the regression analysis model, both the long-term moving vehicle loads and the asphalt concrete (AC) pavement temperature work as the main factors. The monitored data of the long-term moving vehicle loads and AC pavement temperatures from the structural health monitoring systems installed on a Yangtze River cable-stayed bridge are first used to construct the prediction models of the vehicle loads and the AC pavement temperatures. An exponential model is then developed based on the strain measurements to quantify the relationship between daily averaged pavement temperatures, moving vehicle loads (the annual average hourly aggregated traffic volumes (AAHTV) or the annual average hourly aggregated traffic weight (AAHTW)) and the unit vehicle load induced fatigue, which is derived from a nonlinear fatigue damage accumulative model. Further, a limit equation based on the aforementioned exponential regression model and the nonlinear fatigue damage accumulative model for the fatigue life prediction, which takes into account both the traffic conditions and pavement temperature, is developed. Finally, this methodology is employed to predict the fatigue life of the structural details in orthotropic steel decks under different vehicle load growth patterns in a cable-stayed bridge.