Improving the accuracy of structural hot-spot stress approach

Iikka Poutiainen*, Gary Marquis

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review


A method for extending the applicability of the structural hot-spot stress method for fatigue assessment of welded structures is discussed. The structural hot-spot stress method for plate structures, as currently presented in commonly used design guidance documents, cannot account for the effect of weld size, and load carrying fillet welds are assessed using a different S-N curve as compared to non-load carrying fillet welds. This paper presents a proposal to linearize the local stress distribution through the plate thickness in the plane of the weld toe. This proposal considers the forces transmitted by the weld itself. A bilinear stress distribution, which partially captures the local effect of the weld, is derived from the non-linear stress distribution. The non-linear distribution is based on equilibrium and the stress in the fillet weld. A simple procedure is presented to determine the bilinear curve from the nominal weld stress. This is a great advantage in finite element analysis when only nominal base plate stress and nominal weld stresses need to be determined. When compared to the more conventional structural stress approach, the new method also has the advantage that extrapolation is not required. The same weld stresses can also be used in the analysis of the root cracks. The proposed method was scaled to correspond to the traditional structural hot-spot stress method using detailed linear elastic fracture mechanics simulations. The method is only applied to fully load-carrying welds here but can also be used for partial load-carrying welds. Asymmetric splice plate having a fully loaded fillet weld is presented as an example case. The influence of base plate thickness is studied as well.

Original languageEnglish
Pages (from-to)901-905
Number of pages5
JournalSteel Research International
Issue number12
Publication statusPublished - Dec 2006
MoE publication typeA1 Journal article-refereed


  • structural stress
  • hot spot stress
  • fatigue
  • welded joint
  • fillet weld

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