| Due to low weight,high bearing capacity,good applicability and high degree of mineralization,orthotropic steel deck has been widely used in bridge engineering at home and abroad.However,steel decks put into operation in the early years were found to have different degree of fatigue cracks,and the fatigue cracking has become one of the main challenges faced by long-span steel bridges.Supported by the National Key R&D Program of China(2016YFC0701202),the fatigue performance of the vulnerable details of orthotropic steel deck is analyzed,and the method of fatigue crack reinforcement is studied.The main research contents and conclusions are as follows:The wheel-load stress response and fatigue life of ten vulnerable details was investigated through finite element method,the results showed that the longitudinal influence region of rib-to-deck details on and between floorbeams are a span length with one half in front of the details and another at the back.The longitudinal influence region of rib-to-floorbeam details are two span lengths.The fatigue life of nine details is all lower than 100 years,five out of which is less than 10 years.Based on the fatigue test of seven specimens,the fatigue performance of rib-to-deck connection joint was studied.The typical fatigue failure process is divided into three stages: crack initiation stage,stable expansion stage and rapid expansion stage.Most specimens crack at the welding toe of the roof except that one specimen cracks at the welding root of the roof.During the whole loading process,the specimen is in the elastic working state.The stress in the uncracked position increases with the crack tip approaching,the stress decreases after the crack passes,and the stress is completely released after the deck breaks.As the penetration rate of the weld increases,the internal force distribution of the connection between the longitudinal rib and the roof changes,the internal force borne by the roof decreases and that borne by the longitudinal rib increases.After comparing the crack initiation life and fatigue failure life of each specimen with the S-N curve of Eurocode,it is recommended to use S112 curve to predict crack initiation life of rib-to-deck detail.The influence of local and integral reinforcement method to fatigue performance of the vulnerable details was investigated.The result showed that bonding structural steel has a better performance than bonding FRP angle with the same size,and increasing the thickness of reinforcement can improve the efficiency.The reinforcement method with forming steel-UHPC composite bridge deck can significantly improve the transverse stiffness of the steel deck,and reduce the peak load stress and the equivalent stress range of each fatigue vulnerable detail. |
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