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Fatigue cracks in the stiffener-to-deck plate connections of orthotropic bridge decks, initiating from the weld toe or root and propagating into the stiffener or weld throat, are experimentally and numerically studied. A statistical analysis of the structural stress is carried out using the experimental data. Automatic welded specimens show a significantly higher fatigue resistance than manual welded ones for both details of the study. Including results in the literature, the characteristic fatigue resistances appear larger than the values in current standards and range between 100 and 160 MPa. A proposal for the fatigue resistance values is given for design purposes. The effective notch stress, averaged strain energy density factor, and fracture mechanics methods are employed to study the sensitivity of the weld toe and root cracks for different (geometrical) variations, such as the lack of weld penetration. Among them, the fracture mechanics method agrees best with the experimental data. With the increase of weld penetration ratios from 75% to 100%, the fracture mechanics predicted fatigue resistances remain approximately equal for the weld toe cracks and increase for the weld root cracks., Steel & Composite Structures

The notch Effects created by the rough surface of as-built Wire and Arc Additive Manufactured (WAAMed) products may negatively affect the fatigue resistance. This can be prevented by post-production treatments such as machining, but it implies an additional manufacturing step involving costs and time. There is a need to quantify the actual notch Effects of as-built surfaces of WAAMed parts, which can be accomplished via a parameter called fatigue notch factor. This paper focuses on the experimental evaluation of the fatigue notch factor in as-built WAAMed specimens made of AISI 308LSi stainless steel tested with a load ratio of 0.1. Two test series consisting of as-built and machined plain specimens, respectively, have been tested by applying the load perpendicularly to the deposition plane. In this loading configuration, the as-built surface can be regarded as made of periodic notches. A dedicated specimen geometry based on the indications given in the International Standard ASTM E466-21 has been used for the tests. This innovative design allows to induce crack initiation in the periodic notches of the as-built surface while preventing the final fatigue fracture at the first notch root. After the fatigue tests, the fracture surfaces resulting from some specimens have been analyzed using the Scanning Electron Microscope (SEM) to determine the location of crack initiation. As a result of the study, the S-N curves in terms of nominal stress range have been derived and the fatigue notch factor has been determined.

Steel Orthotropic Bridge Decks (OBDs) are widely used in long-span and movable bridges. Fatigue resistance analysis plays an important role in the design or assessment of OBDs. One possible fatigue failure is the crack initiating from the weld root of stiffener-to-deck plate connections at crossbeams. A full-scale experimental investigation in this study using a 20 mm thick deck plate with a dimension of 9.4 m × 5.1 m, including three crossbeams, represents the modern designed OBDs. The experiments show an arrest of crack propagation with a final crack depth of approximately 75% of the deck plate thickness. On the contrary, through thickness cracks develop in deck plates of 10 or 12 mm. Hot spot stress based fatigue detail categories (DC) using various failure criteria derived from the tests. Analysis with the effective notch stress shows that the DC has low sensitivity to the amount of weld penetration. The results of analyses with the eXtended Finite Element Method (XFEM), employed to analyse the fatigue crack propagation path and crack arrest, are in line with the experimental study., Steel & Composite Structures