Calibrated design model for the compression capacity of angle members: Consideration of welded or bolted joint configurations

Due to the commonly eccentric connection on only one angle leg (bolted or welded), additional bending moments are acting on the angle member under compression axial force, leading to a complex load-carrying behaviour with flexural and/or flexural torsional buckling phenomena. Furthermore, type and size of rotational restraints at the member's ends (provided by the adjacent structure) significantly influence the compression capacity of these members. In this article, a recently developed design model for angle members in compression with welded or bolted end connection is presented. The design model considers the accurate rotational spring stiffness of three common joint types. The presented procedure allows for calculating the internal forces based on elastic second-order theory for an individual member with eccentricities, equivalent geometric imperfection and rotational spring stiffness at both ends. The detailed analytical equations for the rotational spring stiffness of all studied joint configurations are summed up. In addition, calibration factors fDi are presented, to get accurate compression capacities with the design model. Finally, the accuracy of the design model for all three studied joint types of angle members with welded connections is shown through comparison with sophisticated finite element calculations, code provisions (EN 1993-1-1, AISC) and experimental tests from the literature.