This work package sets out to derive a set of equivalent mechanical models for bolted connections in moderate to thick high strength steel plates. These equivalent models can be used in large assemblies involving many connections subject to fatigue. Indeed, if a structure contains several dozens of such bolted connections, it becomes prohibitively expensive to build a finite element model containing sub models for each joint. In WP6, the main objective is to replace these complex joints by equivalent joint elements or models which reproduce the global response of the joint under multi-axial fatigue loading conditions. A set of design rules will be derived to dimension bolted joints in HSS applications subjected to fatigue loading.


  • Assess the current state-of-the art of modeling equivalent bolted connections with FEA specifically for moderate to thick high strength steels under fatigue loading conditions and to link these techniques with current standards and generally accepted guidelines. To classify, additionally design and validate computationally efficient and mechanically equivalent FE models for single bolt connections in HSS under both static and fatigue loading.
  • Derivation of correlations and/or analytical relations between the static strength of a HSS bolted connection and its fatigue strength under the same loading mode. This correlation will allow to quantitatively describe the fatigue behaviour of the mechanical joints starting from experimental data on the static strength which is easy to obtain in most cases.
  • Apply and refine the equivalent single bolt model concepts to bolt groups under complex fatigue loading conditions and to assess the accuracy by comparison to detailed numerical models.
  • Optimize (with respect to fatigue) a selected number of complex bolt joints and perform final benchmark tests of the equivalent modeling techniques by comparison with experimental data.
  • Draft a practical methodology or workflow for assessing complex bolted HSS joints under fatigue loading conditions with special attention to the trade-off between modeling effort and accuracy.
  • Derive a set of design rules for the dimensioning of bolted joints in applications involving fatigue of HSS materials. These rules will be governed by material grades and thicknesses, joint dimensions and distances, and type of loading. The definition of safe working limits is also included.