Fatigue strength and crack growth of double-side welded rib-to-deck joint in orthotropic steel decks

Abstract

Fatigue failure in orthotropic steel decks (OSDs) leading to the reduction in service life of bridge structures has been paid much attention. The innovative double-side welded rib-to-deck (DWRTD) joint was proposed to enhance the fatigue resistance of OSDs. In this study, fatigue tests of several specimens of DWRTD joints were conducted by an innovative test setup to reveal the real stress state of DWRTD joints in OSDs. The fatigue resistance of DWRTD joints was estimated by hot spot stress method associated with S-N curve. Beach marks were introduced to record the process of fatigue crack propagation. Furthermore, single-crack and multi-crack propagation simulations were executed based on fracture mechanics to analyze the effect of multi-crack propagation and coalescence on the fatigue life of DWRTD joints. The fatigue test results indicate that the fatigue strength of DWRTD joints satisfies the design category FAT100 (100 MPa at 2 × 106 cycles) in IIW, and the fatigue crack initiation from the interior deck weld toe dominates the fatigue failure of DWRTD joints. The multi-crack propagation and coalescence significantly accelerate the fatigue failure of DWRTD joints, and the fatigue life will be overestimated neglecting the multi-crack propagation.