Abstract：Fatigue cracking of orthotropic steel bridge deck (OSD) is a key problem restricting the sustainable development of bridge engineering. Based on the Shenzhen-Zhongshan link project, the rib-to-deck innovative both-side welded joint and the rib-to-diaphragm innovative welded joint were introduced into the bridge deck, and nine full-scale segment models were designed. Furthermore, the fatigue cracking patterns and fatigue resistance of the rib-to-deck welded joint and the rib-to-diaphragm welded joint were determined by model tests. The initial microcrack scales of the rib-to-deck welded joints were studied by Scanning Electron Microscope (SEM). An equivalent structural stress method was employed to determine fatigue cracking patterns and fatigue resistance of the two details. The results showed that the fatigue cracks of one-side welded joint initiated from the weld root and then propagated along the thickness direction of deck, and its fatigue resistance was 95.1MPa to 98.7MPa. The fatigue cracks of the innovative both-side welded joint initiated from the inside weld toe and propagated along the thickness direction of deck, and its fatigue resistance was 108.5MPa to 123.2MPa. Under the same loading conditions, the fatigue resistance of the bothside submerged arc welding structural details was higher than that of the both-side gas shielded welding structural details. It was found that the initial microcrack size at the weld root of one-side welded joint was noticeably larger than that at weld toe of both-sidewelded joint, and the initial micro-crack size of both-side submerged arc welding was smaller than that of the bothside gas shielded welding. The fatigue cracks of the traditional rib-to-diaphragm welded joint initiated from the weld toe of rib-to-diaphragm welded joint and then extended along the rib, whereas the fatigue cracks of the innovative welded joint initiated from the weld toe of the rib bottom and then propagated along the bottom plate. The crack initiation times were basically the same for the two structural details, but the propagation rate of the traditional one was remarkably higher than that of the innovative one. Test results of fatigue cracking modes of the two details basically varied between ±2σ of the master S-N curve.
