Fatigue Performance of Roof and U-Rib Weld of Orthotropic Steel Bridge Deck with Different Penetration Rates

Forty specimens were tested under different stress amplitudes to study the roof and U-rib weld fatigue performances of orthotropic steel bridge decks, considering different penetration rates and thicknesses. Nominal and hot-spot stresses were measured. The crack propagation and microstructure were analyzed, and the cracked sections were cut out to observe the metallographic means. On the basis of test results, the fatigue life and strength were investigated. In addition, crack-propagation processes and stress-intensity factors were analyzed by the finite-element method (FEM). The results reveal that an increased penetration rate can decrease the crack-propagation rate and enhance fatigue life. An increase in deck thickness can cause a more obvious improvement in slowing the rate of crack propagation and the fatigue life under high-stress amplitudes. A lower penetration rate resulted in a larger decrease in bearing capacity after cracking, especially in a thicker deck. The increased penetration rate contributed to a decrease in the local stress-intensity factor but had little effect on crack angle and path. The fatigue strengths of nominal and hot-spot stress methods were suggested to be 70 and 75MPa, respectively. (C) 2017 American Society of Civil Engineers.