## 5 Non-Uniform In-Depth Residual Stress Field of the Orthotropic Bridge Deck
### Experimental Hole-Drilling Measurements  
Experimental residual stress measurements on an orthotropic steel deck are performed with the incremental hole-drilling procedure according the ASTM standard. The full scale test specimen used for the measurements is shown in Figure 10[17]. The longitudinal stiffeners are welded to the bridge deck plate with twin wire submerged arc welding. The welding can only be executed from the outside of the stiffener since the inside cannot be reached with a welding torch. The parameters of the welding procedure are provided by the manufacturer. The diameter of the electrodes is 2 mm  
Figure 9: Comparison between linear-elastic and elastic-plastic material behavior from 3D models. while the extension of one electrode is 30 mm. The welding is executed with a current op 780 A and a voltage of 29 V. The advancing speed of the welding torches is 950 mm per minute. The welding current flows from the electrode to the base metal. Locations on the top and bottom of the deck plate and on the longitudinal stiffener are evaluated. Strains are measured at incremental depths of 0.05 mm until a final hole depth of 1 mm is reached. A single representative value for the residual stress is selected for each strain gauge rosette in the residual stress distribution into the depth of that particular strain gauge rosette. The near surface stresses are affected by the grinding disc which is used to prepare the surface for the installation of the strain gauge rosette. The residual stress at the final hole depth of 1 mm is considered to minimize the impact of the surface preparation on the residual stress value. A residual stress distribution for the longitudinal and transverse directions can be established in relation to the distance to the weld. The locations of the different strain gauge rosette  
Figure 10: Full scale test specimen (**a**) top view; (**b**) cross section; (**c**) bottom view between two longitudinal stiffeners. A residual stress value is assigned to each measured strain gauge rosette for the transverse and longitudinal directions. This residual stress value is the calculated stress at the final hole depth according the calculation principles of the ASTM standard for both directions. Since the values of the residual stresses vary for neighboring strain gauge rosettes, a distinction is made between compressive and tensile residual stress values. The measured locations are grouped in compressive and tensile zones. The residual stress values assigned to these zones are calculated by averaging the residual stresses of the strain gauge rosettes present in the considered zone. Positive values indicate tensile residual stresses while negative values indicate compressive stresses. In the longitudinal direction, there is a tensile and a compressive residual stress zone present on top of the deck plate. The tensile zone has a value of 64% of the yield strength (f\({}_{\mathrm{y}}\)) while the compressive zone reaches the yield strength. For the bottom of the deck plate, there is a tensile residual stress zone (0.5 \(\times\) f\({}_{\mathrm{y}}\)) present in the longitudinal direction. On the stiffener, there is a small tensile yield stress zone present near the weld which is followed by a compressive zone (0.17 \(\times\) f\({}_{\mathrm{y}}\)) and a tensile zone (0.13 \(\times\) f\({}_{\mathrm{y}}\)). For the transverse direction, two tensile zones and a compressive zone are recognized on the top of the deck plate. In between the two welded webs of the stiffener, an average tensile residual stress of 67 MPa exists. Near the weld location on the deck plate, there is a compressive zone with an average residual stress equal to 0.42 \(\times\) f\({}_{\mathrm{y}}\). Another tensile residual stress zone exists at the right-hand side of the weld region on the deck plate. On the bottom side of the deck plate, an average tensile residual stress equal to 70% of the yield strength exists. For the longitudinal stiffener, there is a tensile residual stress zone present near the weld.