Fatigue Capacity of Headed Shear Studs in Composite Bridge Girders: Fid-Bau Portal

Fatigue Capacity of Headed Shear Studs in Composite Bridge Girders

Ovuoba, B. / Prinz, G. S.

Shear connectors are commonly used in steel bridges to join the concrete deck and steel superstructure, providing a mechanism for shear transfer across the steel–concrete interface. The most common type of shear connector is the headed shear stud. In the current American Association of State Highway and Transportation Officials (AASHTO) LRFD Bridge Specifications on composite design, shear stud fatigue often governs over static strength, and a large number of shear connectors often result. The stud fatigue capacities presented in the AASHTO standard are largely based on a limited sample of composite fatigue tests performed in the 1960s, with limited fatigue test data at lower stress ranges leading to a somewhat arbitrary constant amplitude fatigue limit (CAFL). This often governs the composite design for bridges with moderate-to-high traffic demands. This paper presents results from an experimental and analytical study of the fatigue behavior of headed shear studs to address the lack of existing experimental data near the assumed CAFL and to better characterize the effects of fatigue uncertainty on predicted response. Results from composite push-out specimens tested at low stress ranges of between 30 and 60 MPa (4.4 and 8.7 ksi) suggest a fatigue limit of 44.8 MPa (6.5 ksi), which is near the existing limit of 7 ksi. Recommendations for modifying the existing AASHTO finite life shear stud S-N fatigue capacity curve are proposed.