Analytical frame approach for the axial stiffness prediction of preloaded T-stubs

• A model for the prediction of axial stiffness of preloaded T-stubs is proposed.
• An advanced 3D finite element modelization has been developed.
• The parameters that affect the behavior of preloaded T-stubs are identified.
• A preloaded T-stub effective width has been proposed for stiffness calculations.

The behavior of beam-to-column bolted connections can be predicted by means of the component approach, included in the Eurocode 3. This method accounts for any bolted connection typology once the basic components are identified and modeled. Many of these components are represented using the so-called equivalent T-stub. In some cases, these joints may need to be preloaded in order to hold fatigue loads or even just to increase the connection stiffness.In this paper, an equivalent frame model, which implicitly includes the bolt, is presented to predict the axial stiffness of preloaded T-stubs. This proposal, designed for hand calculation, takes into account compatibility requirements and prying forces. Besides, an advanced 3D finite element (FE) model of a representative T-stub test is done to characterize the deformation response and the boundary characteristics related to preloading, in order to support the analytical proposal. Furthermore, an effective width for stiffness calculation is suggested, based on an extensive plate FE parametric study.Results are validated by comparison with experimental data from the literature.