PSI - Issue 57

9

Mladen Lukić et al. / Procedia Structural Integrity 57 (2024) 550 – 559 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

558

Fig. 9. Flange thickness tapering in girders: (a) tapering to the outside, (b) tapering to the inside, (c) centric tapering (both sides tapered)

The recommended magnification factors k 1 and stress concentration factors k f as specified by Annex D of prEN 1993-1-9 (2022) enable practitioners to account for stress raising effects in the form of modified nominal stresses in a simple way. Alternatively, finite element methods can be applied to take the stress raising effects into account. 7. Guidance on stress ranges in preloaded bolts (Annex E) Annex E contains supplementary guidance to determine nominal stress in preloaded bolts and rods subject to tension. The presented procedure is a simplified calculation method for preloaded bolts or rods under a centrically applied external tensile force accounting for the beneficial influence of preloading. Alternative, more detailed, calculation methods in combination with prEN 1993-1-14 (2022) are also possible with relevant reference publications mentioned in Annex E. 8. Fatigue design of welded joints subjected to High Frequency Mechanical Impact treatment (Annex F) Annex F defines the application requirements of post-weld treatment of specific constructional details through qualified HFMI technologies, to enable the beneficial effect on the fatigue resistance to be taken into account forthe fatigue verification. This annex contains two specific subsections on the requirements for application to link with execution and quality control standards, and on the treatment of variable amplitude loading to allow for proper treatment of mean stress effects. The annex is based on international research works that are summarized in an IIW recommendation (Marquis et al., 2016) and more recently a developed DASt-Richtlinie 026 (2019). Only constructional details with potential fatigue cracking from the weld toe and where extensive research has been conducted are appropriate to benefit from HFMI treatment effects. In order to benefit from the HFMI treatment, in cases where the fatigue action effect is defined by an equivalent nominal stress range, the latter has to be modified with the factor λ HFMI considering the mean stress effect in a spectrum. The study by Al Emrani (Shams-Hakimiet al., 2021) shows that this factorcan be expressed in function of the ratio between stress under self-weight to maximum stress range in the case of road bridges under heavy traffic. Without direct calculation, it is conservative to assume λ HFMI = 2,0. 9. Summary All European design standards, including EN 1993-1-9 (2005), are currently in a revision phase, which will culminate in the next generation of Eurocodes. Since 2021, draft standard prEN 1993-1-9 (2022) has been available, which the CEN member states will vote on in the near future. This paper highlights the most significant changes in comparison to EN 1993-1-9 (2005) with the main goal of informing the interested practitioners.