# Fatigue Performance of Different Rib-To-Deck Connections Using Traction Structural Stress Method
## 3 Fatigue Performance of Rib-To-Deck Connection Types in Orthotropic Steel Bridges
### Comparative Results of Three Typical Connections and Discussions
The stress distribution was non-uniform with the stress concentration at the connection of the rib-to-deck and crossbeam. The shear stress changed in the reverse direction at the middle position. The minimum normal stress at both ends of the Double-Weldline2 was 27.8 MPa. The normal stress increased gradually from the side to the middle of the weld seam and the maximum stress in the middle section was 38.8 MPa. The direction of the shear stress of the weld seam was modified. The trends of the equivalent structural stress and stress components of Double-Weldline3 and Double-Weldline4 were similar to that of Double-Weldline2. The maximum of the normal stress at the bottom side of the bridge deck decreased by 10.6% compared to the traditional weld seam. The normal stress at the top side of the bridge deck decreased by 29.0% and the normal stress at the bottom side of the bridge deck decreased by 17.5%. The comparative results indicated that the equivalent structural stress of the bridge deck with traditional weld seam was more significant when compared to the bridge deck with double-sided weld seam. The fatigue performance of the bridge deck with double-sided seam was much better than that of the bridge deck with traditional weld seam. Figure 13: Mises stress of the bottom side of the top flange of the double-sided weld seam, (**a**) Mises stress diagram of the bottom side of the bridge deck (Pa). (**b**) Fatigue cyclic life of the connection of the rib-to-deck, 1 the number in the contours is the base 10 log of the contour line. Figure 14: _Cont._  
It can be concluded that the bottom side of the bridge deck was mainly subjected to tensile stress with significant normal structural stress. The fatigue performance of the connection of the bridge deck and U-rib was influenced largely by the type of the weld seam. Figure 15 shows the equivalent structural stress of various weld seams of the bridge deck with double-sided weld seam. The trend of normal structural stress of Double-Weldline1 was opposite to that of the other three weld seams. The maximum normal stress at both sides of the Double-Weldline1 was 30 MPa and the stress gradually decreased to the middle of the weld seam. The minimum normal stress is 25.2 MPa. The normal stress increased reversely compared to the other three seams and remained uniform. The trends of the equivalent structural stress of Double-Weldline2 and Double-Weldline3 were similar and the normal stress values were close to each other. The normal stress increased gradually from the side of the weld seam to the middle section and the growth rate increased gradually. The maximum normal stress was 38.74 MPa and 38.68 MPa, respectively, for Double-Weldline2 and Double-Weldline3. The normal stress at the middle section decreased slightly. Figure 16 shows the equivalent structural stress of various weld seams of the bridge deck with various weld seam. The increase of stress in the inner weld seam of the rib-to-deck connection optimizes the distribution of the equivalent structural stress. The fatigue failure location was shifted from the  
Figure 14: Equivalent structural stress of the weld root and weld toe of double-sided weld seams. (**a**) Equivalent structural stress of Double-Weldline1, (**b**) equivalent structural stress of Double-Weldline2, (**c**) equivalent structural stress of Double-Weldline3, (**d**) equivalent structural stress of Double-Weldline4. Figure 15: Equivalent structural stress of weld seams of bridge deck with double-sided weld seam. -weld root of the outer weld seam to the weld toe of the inner weld seam demonstrating the effect of the crossbeam.