Abstract
This study numerically investigates the limitations of structural hot-spot stress (SHSS) methods and proposes a guideline for the calculation of hot-spot stresses, which can be used for the better evaluation of fatigue-related problems. Four different SHSS evaluation methods have been applied to the rib-to-deck (RD) welded joint in orthotropic steel deck (OSD). These methods are used to calculate SHSS at this critical joint utilizing finite element analyses (FEA) based software Siemens NX.12. The limitations and the accuracy of these methods have been observed under different element types and meshing techniques. Moreover, the effect of the nodal-averaging feature is being studied. Two types of governing stresses are produced by the application of Eurocode fatigue load model-4. Essentially, the bending in deck-plate produces highly non-linear stress at the deck-toe, and the membrane effect in rib-plate generates linear stress at the rib-toe. Guidelines are proposed considering different parameters on these two stress states by applying SHSS evaluation methods. In comparison to other SHSS approaches, the International Institute of Welding (IIW) quadratic stress extrapolation (QSE) method shows better results for solid single-element, and the American Society of Mechanical Engineers (ASME) through thickness stress linearization (TTSL) method stands out in solid cubic-mesh technique. In general, shell elements have more consistent SHSS results as compared to solid elements for both stress states.
Highlights
Fatigue failure of welded joints is a highly localized phenomenon which normally comprises crack initiation and propagation near weld-toe, while design guidelines given in the different codes roughly incorporate local stresses
The nodal averaging feature did not have much influence on rib-toe results, while the deck-toe showed a significant decrease in structural hot-spot stress (SHSS) results in 2.0 mm elements (2-CH20/8), which was more prominent in the 2-CH8 element
For 1/2-CH8 elements, the 2-CH8 element gave higher stress results at 0.4t as compared to the 1-CH8 element, which increased SHSS for quadratic stress extrapolation (QSE) and linear stress extrapolation (LSE) 410 methods, while in the LSE 515 method, the stress results converged at 0.5t, which is why SHSSs for both mesh sizes were identical in this method (Figures 8a–f and 9a,b)
Summary
Fatigue failure of welded joints is a highly localized phenomenon which normally comprises crack initiation and propagation near weld-toe, while design guidelines given in the different codes roughly incorporate local stresses. This guide provides an overview for the fatigue life assessment of welded connections using different structural hot-spot stress (SHSS) methods and provides application with examples using FEA [1] These guidelines are not widely accepted in the field or the design office, because there are some uncertainties present in their usage. The testing engineer in the field and the structural designer at the office must have some well-established methods for the measurement of local strains and stresses to evaluate the fatigue life of the structures To overcome these uncertainties, an extensive study was carried out by considering a complex welded detail in an orthotropic steel deck (OSD) that connects the steel deck to the longitudinal-rib and usually known as a rib-to-deck (RD) joint [9,10]. The details of the methods used in this study are given
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