New developments in the design of bolted or welded single steel angle members in compression

The practical design of single steel angle members in compression has to cover multiple effects. Due to the commonly eccentric connection on only one angle leg (bolted or welded), additional bending moments are acting on the member, leading to a complex load carrying behaviour with flexural and/or lateral torsional buckling phenomena. Furthermore, type and size of rotational restraints at the member's ends (provided by the adjacent structure) significantly influence the compression member capacity of these members.

Within this paper, a recently developed design approach for angle members in compression is introduced. The presented method allows for calculating the internal forces and the compression member capacity based on elastic second order theory for an individual member with eccentricities and rotational spring stiffness at both ends. This calculation can be carried out by means of conventional structural analysis software. Detailed analytical models for the estimation of appropriate spring stiffness values are presented for several practical applications in buildings with two-bolt connections at both member's ends.

Subsequently, the new design method is enhanced by means of additional formulae for angle members bolted to transverse stiffeners of I-shaped girders and for angle members welded to the adjacent structure at one angle leg only. Detailed background information on the derivation of these newly developed formulae is given. Finally, the accuracy of the design model for this enlarged range of application is shown through comparison with sophisticated finite element calculations.

Learning Objectives:
Recognize the influence of boundary conditions on member capacity of single steel angles.

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