Buckling Strength of Single Angle Struts Part 2: Angles Connected by One Leg at Both Ends

A single angle strut connected at both ends by one leg is simple in execution, but complex in behavior. As a monosymmetric section, the angle is subjected simultaneously to compression, biaxial bending and torsion. Furthermore, there exist at the two ends rotational restraints whose rigidity depends on the member arrangement and joint detailing of the truss. So, a rigorous solution of the bearing capacity of such angle is very difficult to establish. The common practice in design work is to transform this complex problem into the buckling of an axially compressed strut, hinged at both ends, by taking an equivalent slenderness ratio. In this study, new formulas for this equivalent slenderness are suggested, where a concept of partial adjustment is introduced so that they apply to angles of high strength steel as well as to those of low carbon steel. The detrimental effect of torsion on the strut capacity is not negligible when the angle has slender leg, especially for high strength steel. Formulas of reduction factor to the member yield strength are proposed in this regard and are given as a function of the flat width-thickness ratio instead of the overall width-thickness ratio of the leg. These formulas, in conjunction with those for equivalent slenderness, correlate well with the test program of angle struts, steel grade 460 MPa. Lastly, limitations to the formulas of equivalent slenderness are discussed.