# Residual Stress Relaxation of DRWDs in OSDs under Constant/Variable Amplitude Cyclic Loading
## 2 Welding Residual Stress Distribution  
### Welding Residual Stress Measurement  
An experiment on full-size OSD specimens was carried out to investigate the welding residual stress of DRWDs of a Q345 steel deck. In this study, the Jiangyin Yangtze River Highway Bridge, the first extra-large steel box girder suspension bridge with a span of kilometers in China, was taken as a case study. Thus, the structural style and dimensions of the specimen in this paper is made referring to the OSDs in main girders of this bridge. Figure 1 shows the cross section and dimensions of the OSD test specimen. It is seen that the specimen was 1200 mm long, 300 mm wide, and consisted of one top deck and two U-ribs. The thickness of the top deck was 12 mm, and the thickness of the U-ribs was 6 mm. The material of the specimen was steel of Q345 quality, which implies a yield strength (\(f_{y}\)) of 345 MPa. In the welding, CO\({}_{2}\) gas shielded welding was adopted and the groove angle was 50\({}^{\circ}\)\(\pm\) 5. The arc voltage and current were set to 29 \(\pm\) 1 V and 300 \(\pm\) 100 A, respectively. The welding speed was 10 \(\pm\) 1 mm/s. A flux-cored wire (E501T-1) diameter of 1.6 mm was used for the welding stick. The transverse welding sequence was 1 st weld to 2 nd weld to 3 rd weld to 4 th weld, and the longitudinal welding sequence remained consistent, from Z = 0 to Z = 300 mm.  
In this paper, the blind hold method [21; 22] was used to measure residual stress. As shown in Figure 2, the test drilling equipment was an electric discharge drilling machine with a bore diameter of 1.5 mm and a hole depth of 2 mm; the strain gauge used was a three-dimensional rosette gauge, which is a dedicated gauge for testing residual stress. The release strain was collected by a static strainometer.  
Figure 1: Orthotropic steel deck (OSD) experimental specimens: (**a**) space diagram and measurement paths; (**b**) cross section and dimensions (units: mm).  
As illustrated in Figure 3, the length direction of OSD experimental specimen is set as the \(X\)-axis, the width direction as the \(Z\)-axis, and the height direction as the \(Y\)-axis, which is consistent with the following finite element model (FEM). To facilitate the deployment and wiring of the strain gauge, the distance between measurement points was set to 30 mm. The layout paths of the residual stress measurement points and the hole drilling locations of various paths are presented in Figures 4 and 5. The length of the model along the longitudinal direction (the \(z\)-axis in Figure 4) is 500 mm. The measurement points of Paths P1 and P2 are laid out along the length of the deck. As shown in Figure 4, Path P1 is laid out on the top surface along the length of the deck plate (B1-B31), and Path P2 is laid out on the bottom surface of the deck plate (D1-D8). Paths P3 (P4). P5, and P6 are laid out along the width of deck plate and are approximately 135 mm, 465 mm, and 1065 mm away from the arc striking position, respectively. Paths P4 and P5 are located at the weld center on the top surface of deck plate (Z1-Z12). Paths P3 and P6 are located at the weld root on the bottom surface of the deck plate (Z13-Z24).  
Figure 3: Diagram of the measurement paths: (**a**) cross section diagram; (**b**) plan diagram (units: mm).  
Figure 2: Experimental device: (**a**) test drilling equipment; (**b**) electric pole; (**c**) strain gauge.  
Figure 4: Diagram of the measurement points of layout paths: (**a**) cross section diagram; (**b**) plan diagram (units: mm).  
Figure 5: Hole-drilling locations of various paths: (**a**) P1, P4 and P5; (**b**) P2, P3, and P6.