Issue 45

L.M. Viespoli et alii, Frattura ed Integrità Strutturale, 45 (2018) 121-134; DOI: 10.3221/IGF-ESIS.45.10 127 The mean SED is then obtained simply by dividing by the volume of the element. The key point in the computation is the dependence of the energy on the displacements and the stiffness. A continuum modeled with a coarse mesh will result having higher stiffness and lower displacements. As shown in the mesh refinement analysis, these two effects are balanced and allow to have a very precise estimate of the mean SED with a reduced number of elements. N OMINAL S TRESS A PPROACH or the Nominal Stress approach, the stress considered does not take in account the micro-geometric characteristics of the joint, but only its macro-geometric shape. In particular, for the case considered, the simple plain shape allows to a fast individuation of the nominal stress, being this coincident with the remote stress applied to the main plate. Longitudinal fillet welded gusset of length l. Fillet weld around end. FAT class for steel l<50 mm 80 l<150 mm 71 l<300 mm 63 l>300 mm 50 Table 1 : Top: FAT classes for detail 521 page 65 IIW document depending on longitudinal attachment length [2]. Bottom: S-N fatigue curves of different fatigue classes for the fatigue life assessment of structural steel welded joints, according to the IIW document [2]. As indicated on page 65 of the IIW document, having the l dimension in the range between 50mm and 150mm, the detail belongs to the fatigue class FAT 71 for steel. The estimated fatigue life for the joint subjected to a nominal stress is easily computed according to the nominal stress method as:       m m ref ref N N N 0 F