Experiment on fatigue behavior of rib-to-deck weld root in orthotropic steel decks

• Structural response of field measurement and fatigue tests.
• Residual stress measurement in the vertical deck.
• Quantitative analysis of crack patterns.
• Study of fatigue behaviors of weld root depending on the loading and welding conditions.

This study experimentally investigated the fatigue behavior of the weld root in orthotropic steel decks stiffened with U-ribs in relation to the loading conditions and welding details. To examine the structural response and local stress near the welded joint, field loading tests, measurement of residual stress, and fatigue tests were carried out. A total of 12 specimens were manufactured, and the fatigue tests were performed by simulating the double tire loading of an actual vehicle. The welding residual stress distribution at the root was examined to understand the mechanism of root crack initiation and propagation behavior. Thus, fatigue behavior of the root crack was investigated and evaluated by considering different stress ratios and weld penetration rates. Based on the fatigue test results and crack patterns, it was revealed that both tensile stress and stress range could affect the root crack initiation. However, the tensile stress rather than the magnitude of stress range would be the effective stress after a crack initiated, and it was seen to be an important factor for root crack propagation. In addition, a penetration rate in the range of 0% to 75% was beneficial for fatigue durability of this structural detail.