Members of Simpson Gumpertz & Heger’s (SGH) structural engineering and structural mechanics team have published two research articles comparing conventional and vanadium steel in the latest issue of the American Institute of Steel Construction’s (AISC) Engineering Journal. SGH’s Mohamed Talaat, Mark Webster, Ronald Mayes, and Frank Kan – along with Ahmet Citipitioglu, formerly of SGH and now with TAV Construction in Istanbul, Turkey – analyzed the performance of high-strength, low-alloy vanadium (HSLA-V) steel in double-angle compression members. HSLA-V steel is generally stronger than conventional steel, which results in potentially lighter and more slender structural components, making them more susceptible to buckling in compression. The authors also assessed the 2010 AISC and Steel Joist Institute (SJI) design specification provisions for compression buckling of steel double angles, and recommended changes to these provisions.
In “Buckling of Conventional and High-Strength Vanadium Steel Double-Angle Compression Members: Computational Parametric Study,” the authors tested a series of conventional and HSLA-V steel double-angle compression members to compile an experimental database, and developed a modeling approach using finite element software to simulate buckling response. The finite element models accurately predicted the buckling strengths of the tested members. The authors then used an analytical parametric study to extend the predicted buckling strength evaluations to a large number of double-angle sizes and lengths. The authors recommended that the SJI specification adopt the modified slenderness ratio provision in the 2010 AISC specification, and found that the 2010 AISC lateral-torsional buckling provisions are overly conservative when applied to double-angle compression members with low slenderness ratios. The SJI specifications now adopt these modified slenderness ratio provisions. AISC 2016 specifications have significantly modified the lateral-torsional buckling provisions.
In “Buckling of Conventional and High-Strength Vanadium Steel Double-Angle Compression Members: Computational Parametric Evaluation of Slenderness Modification Factors,” the authors further examined double-angle compression members with a focus on open-web joist applications. The study evaluated the effect of the local angle leg slenderness ratio (Q-factor) on the accuracy of the AISC 2010 buckling equations for a range of specimen sizes and material strengths. The investigation found that these equations systematically produce non-conservative predictions for elements with high local slenderness ratios (i.e., low Q-factors). The authors proposed and assessed two alternative modifications to the Q-factor definition and recommended one of them for adoption by the AISC specification in conjunction with the recommendations made in the first article.