# Stress Behaviors at Rib-to-Floorbeam Weld and Cutout Details under Controlled Truck Loading
###### Abstract  
The rib-to-floorbeam (RF) connection is the most complicated joint in orthotropic steel decks (OSDs), where four fatigue-prone details are created, i.e., the RF at the rib side (RF-R), RF at the floor beam side (RF-F), RF at the rib wall (RF-W), as well as the floor beam cutout detail. In order to clarify the behavior of those details under the passage of trucks, a controlled truck loading test and finite element analysis (FEA) are performed at various typical transverse loading locations on a newly built long-span cable-stayed bridge. The research finds that, in the bridge transverse direction, stresses at the four details presented significant local effects. Only when these details are underneath the deck plate covered by the wheel patch a notable stress can be produced at these details. In the bridge longitudinal direction, the wheel loading effect at the four details can be discerned only when the wheels load on the deck supported by their adjacent floor beams. The results find that, under wheel loading, the stress ranges at the RF-R, RF-F and Cutout details are compressive, while the stress at the RF-W detail is in tension. The riding-rib-wall loading is the most critical transverse loading location for the RF and Cutout details, and the RF-W is the most critical fatigue detail in the RF connection. The FEA indicates that, due to offset of wheel loads, floor beams may suffer from severe out-of-plane bending, while ribs may experience notable warping and distortion. Under the passage of the tandem axles, the individual axle cannot be identified, and only one stress cycle is produced at the four details. orthotropic steel decks; stress behavior; fatigue detail; controlled truck loading; finite element analysis +
Footnote †: journal: Medical  
most complex connection on the OSDs, the RF weld creates four fatigue-prone details that present a significant concentration and highly complicate stress behavior under wheel loads. Under the passage of truck loads, the ribs generate a differential vertical deflection in the bridge transverse direction. As supported and constrained by the floor beams, this kind of deflection results in twisting and warping effects in the rib wall, which eventually produce a highly coupled deformation both in the ribs and the floor beams [16; 17]. Consequently, complex stress generates at the RF weld and nearby Cutout details with a significant stress concentration. The observed fatigue cracks are reported at the rib side of the RF weld (RF-R in short), at the floor beam side of the RF weld (RF-F in short), at the wrap-around weld of the RF weld (RF-W in short), as well as at the floor beam cutout (Cutout in short), as, respectively, shown in Figure 1.  
Compared to the understanding of the stress behaviors at the RD details, the stress behaviors at the four details under truck loads are still not clear. [PERSON] [18] studied the stress and deformation at the RF-W detail due to the Poisson's effect of the rib wall at its intersection with floor beams, and analytically derived the secondary stress at the RF-W detail. [PERSON] [19] carried out OSD panel model tests and FEA to study the stress behaviors and fatigue cracking mechanism of RF details by using theory of strain energy. The research indicated that fatigue cracks were initiated at the weld toe of the RF joint with an inclined angle. [PERSON] [20] accomplished a fatigue loading test on a full-scale panel model. The results found that the fatigue cracking could occur at the Cutout detail even though compressive stress is always measured at this detail under wheel loads. It implied that high residual stress existed at the Cutout detail and could highly contribute to cracking at this detail. Numbers of large-scale specimens were tested by [PERSON] [21] to explore the failure process of RF details.