Abstract
This study investigates an analytical beam model to improve the analyses of welded thin plates with welding-induced curved distortions. The model addresses the rigidity of a butt-welded joint and its effect on plate bending and structural stress by including a rotational spring at the welded end. The spring rotational stiffness, ka, is replaced by the fixity factor, ρa. The validity of the model is based on the assumption of small displacement and moderate rotation of the mid-plane of the welded plate. Using the Finite Element Analysis of a two-dimensional model, a semi-analytical method for the fixity factor computation is developed. Compared with the numerical analysis, the beam model showed a maximum error of 3% in deflection and hot-spot structural stress. Results suggest that the fixity factor is mainly dependent on the width of the weld bead and the far-end constraint. The introduction of ρa can improve the analytical solution by 9% in the evaluation of the hot-spot structural stress. Neglecting the non-ideal joint rigidity may lead up to 54% underestimation in terms of fatigue life, when the S–N curve slope, m, equals 5. However, the relevance of ρa decreases for increasing geometric slenderness of the welded plates.
Highlights
Lightweight design is essential in different engineering fields where structural optimisation aims at reduced economic and environmental impact, whilst enhancing the technical performance [1].Thin-walled structures made of high-strength steel are an attractive solution to achieve the lightweight design in the shipbuilding industry, where the use of steel is well-established in the manufacturing process
The present study investigated an analytical beam model for the analysis of thin plate butt-welded joints with an initial curved distortion
A rotational spring allowed the 1D beam model to account for the rotational rigidity of the butt-joint in terms of a fixity factor ρa
Summary
Lightweight design is essential in different engineering fields where structural optimisation aims at reduced economic and environmental impact, whilst enhancing the technical performance [1].Thin-walled structures made of high-strength steel are an attractive solution to achieve the lightweight design in the shipbuilding industry, where the use of steel is well-established in the manufacturing process. For an efficient and flexible routine at the early design stages, the current recommendations for the fatigue assessment of welded components provide analytical solutions based on the nominal or structural hotspot stress approach [6,7]. The current solutions for the km factor account only for a flat distortion, i.e. for a global angular misalignment that is constant between plate supports [8]. For large structures like passenger ships, a time-consuming FEA is highly inefficient in the early stages of the design process. For these reasons, the shipbuilding design standards are still preventing the use of thin plates, i.e. plates with t ≤ 5 mm [10]. The need for improved analytical models emerged especially in the shipbuilding field, the study concerns any application of thin-plate butt-welded joints with a curved initial distortion
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