Fatigue Behavior of the Group Stud Shear Connectors in Steel-Concrete Composite Bridges

Clustering stud shear connectors with a narrow spacing to form the group studs is useful for concrete slab prefabrication in steel-concrete composite bridges; however, the group studs fatigue design has not been specified in detail so far because the related tests and results are not enough. In this case, 13 corresponding cyclic push-out tests were executed. The test results showed that the stud root fracture and the nearby concrete damage were the main fatigue failure modes. Arranging studs in a group made the cyclic stud stiffness degradation and the slip creep develop faster, thus lowering the stud fatigue life. Moreover, the group stud fatigue lives as well as some other related literature results were compared with the S-N curves of AASHTO, Eurocode, and Japan Society of Civil Engineers (JSCE) codes, which are mainly for one single stud. In general, the evaluations based on the Eurocode and AASHTO were relatively conservative. The JSCE evaluation may have less safety redundancy compared with the other two specification-based estimations. Furthermore, a parametric analysis was executed for understanding the mechanism of the group arrangement effect on the stud fatigue behavior. The severer fatigue damage accumulation and uneven distribution among the studs in a group were considered to be the main unfavorable factors in the fatigue behavior.