Equivalent Vehicle Model Based on Traffic Flow of Long-Span Steel Box Girder Bridge

Fatigue vehicle load is essential for fatigue analysis, whose accuracy is directly associated with fatigue design. With the development of society, traditional fatigue vehicle load may fail to reflect modern traffic conditions, especially for transportation hubs in developed areas. Based on traffic flow data of a long-span steel box girder bridge, statistical analysis is performed and the two types of standard vehicle load are equivalent. Further, fatigue characteristics and fatigue life of two types of welded connection are compared based on the equivalent structural stress method. As a result, 2-axle vehicle takes the largest proportion, and the overload ratio of a 6-axle vehicle is the highest. Compared with fatigue vehicle load III, there should be a correction coefficient 1.89 and 2.30 for equivalent vehicle load based on average traffic flow and heavy lane traffic flow, respectively. For a single-side welded connection and a double-side welded connection, the equivalent structural stress will increase by 81.0%-131.2% for positions of concern when considering heavy lane traffic flow, which is about 21% higher than results considering average traffic flow. In addition, the fatigue life of these concerned positions will encounter a dramatic decrease. Fatigue life of the most unfavorable position is 492.4 years and cracks will occur in 90.0 years based on fatigue vehicle load III. However, it will decrease to 42.3 years and 7.7 years, respectively, when considering the traffic flow of the heavy lane.