Vehicle Load Spectrum and Fatigue Vehicle Model of a Long-Span Concrete-Filled Steel Tube (CFST) Arch Bridge Based on Measured Data of Weight-In-Motion System

Highway traffic load, speed, and volume have been increasing continuously over the years. Because of its special structural form, the fatigue problem of a long-span concrete-filled steel tube arch bridge becomes more and more serious. To research the vehicle load spectrum and fatigue vehicle model of a long-span concrete-filled steel tubular arch bridge, the traffic data of the arch bridge were collected using the weight-in-motion system. The vehicle type and vehicle load in the actual traffic flow have strong stochastic characteristics, which cannot be directly applied. Therefore, according to the measured data, 10 representative models are proposed to facilitate the classification and screening of vehicle data. The wheelbase, mass, axle load, and overload data of the representative vehicle types were analysed, and the axle load distribution characteristics of vehicles in different lanes were studied. It is found that the vehicle load is not uniformly distributed in different lanes but concentrated in one lane. Moreover, a vehicle load spectrum for the fatigue assessment of the long-span concrete-filled steel tubular arch bridge is proposed. Based on the fatigue damage equivalence principle, a fatigue vehicle model and a simplified fatigue vehicle model of bridge heavy-duty vehicles are proposed. Compared with the model in the AASHTO specification, it is found that the weight of the local fatigue vehicle load model is 15.1 t heavier than the vehicle model given in the specification. This study could be further referenced in bridge-fatigue life prediction, management and maintenance, etc.

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