Effects of full internal bulkheads on fatigue behaviors of orthotropic steel decks

Abstract

To investigate the effects of full internal bulkheads (FIBs) set inside the ribs on the fatigue behaviors of rib-to-floorbeam (RF) details, rib-to-deck (RD) details, and cutout details in orthotropic steel decks (OSDs) and determine whether new fatigue-prone details will be produced, a field monitoring test was conducted, and OSD models with and without FIBs were developed. The study found that in the OSD with FIBs, the stress amplitudes of the RF-F (RF weld on the floorbeam side) and RF-W (RF weld at the rib wall) details were significantly higher than those of the RF-R (RF weld on the rib side) detail, which were more prone to fatigue problems. The FIBs combine the floorbeam with the ribs, which can significantly enhance the in-plane stiffness of the ribs and make the floorbeam function as a solid-web beam rather than a Vierendeel beam. The stress transmission paths at the RF connection are changed by FIBs—particularly at the RF-W and cutout details. The FIBs cause significant improvements at the RF and cutout details but do not affect the stress response of RD details. The RF and cutout details have infinite fatigue life, with the local stiffness enhanced by the FIBs, but the RD details have a finite fatigue life, as the FIBs are far from the RD details. The rib-to-bulkhead (RB) details have the maximum stress at the bottom of the ribs, where the stress outside the rib is higher than that inside, indicating that the fatigue assessment of RB details can be conducted using the stress measured outside the ribs.