The influence of rib stiffeners on the response of extended end-plate joints

The presence of rib stiffeners in extended end-plate joints influences the yield line distribution in the tensile zone of the connection, the depth of internal lever arm as well as the resistance of compression components of the joint. In addition, the stiffeners may affect the plastic rotation capacity of the connected beam in both monotonic and cyclic regime. The current EN1993:1-8 (2005) gives limited recommendations on these issues, while EN1998-1 (2005) does not provide any detailing rules to enforce ductile cyclic response when rib stiffeners are adopted in end-plate connections. In order to investigate these criticisms, extensive parametric finite element simulations were carried out and the obtained results are described and discussed in this paper. The main analyzed parameters are the thickness, the slope (i.e. the depth to width ratio), and the constructional imperfections of the rib stiffeners for different beam-to-column assemblies alternatively designed with full and partial strength connection. The monitored response from monotonic and cyclic analyses allows characterizing the yield line distribution and the variation of internal forces into the rib and the bolt rows. The evolution of the internal lever arm of the connection, the out-of-plane bending and torsional moments developing when the connected beam experiences large plastic rotations as well as the forces acting on lateral torsional restraints are also investigated.