Coupled fatigue behavior of the steel deck plate in lightweight composite bridge decks

Steel-ultrahigh performance concrete (UHPC) lightweight composite deck (LWCD) is a new countermeasure against fatigue issues for orthotropic steel decks (OSDs). While fatigue response of the steel deck plate in LWCDs is complex: except for normal stress ranges developed in steel deck plate, shear stress ranges are generated in headed stud shear connectors, so the steel deck plate at stud root position is under a complex coupled fatigue response. This paper aims to reveal the coupled fatigue behavior of the steel deck plate in LWCDs. First, three OSD-UHPC composite beam specimens were tested under cyclic flexural loads and the steel deck plates were acted by both normal and shear stress ranges. The tests indicate that although the equivalent fatigue stress ranges in the steel deck plate exceeded the fatigue strengths specified in the Chinese design code for steel-concrete composite bridges, the steel deck plate at stud root position did not develop fatigue failures, indicating that the coupled fatigue strength specified in the design code is applicable for LWCDs. Next, an FE analysis was performed to reveal the coupled fatigue response of the steel deck plate in the LWCD. The distribution of the index values reflecting the coupled fatigue effect was obtained, and the maximum value of the coupled effect was S-max = 0.85, which is lower than the limit value (S-lim = 1.3), implying that the steel deck plate at stud root position should be safe under coupled fatigue actions. Further, a parametric analysis was accomplished to reveal the influence of primary parameters on the coupled fatigue effect.