Effect of accidental joint eccentricity on the behavior of concentric braces

Concentric braces are designed with the assumption that their joints are concentrically loaded, meaning that the axes of the connected members intersect at a working point within the joint region. To avoid eccentricity at a joint, the load path from each member framing into the joint should intersect at this working point, ensuring alignment within the joint region. However, in real structures, compression members are not perfectly straight, aligned, or concentrically loaded as assumed in design calculations. In AISC 360-22 and EN 1993-1-1, certain safety factors are applied to account for uncertainties related to initial imperfections in concentric braces. However, these safety factors are uniform across all slenderness ratios, and it is unclear up to what level of eccentricity they ensure safety. To address these shortcomings, an experimental and numerical program was conducted to examine the effect of various accidental eccentricity conditions on the behavior of concentric braces. The results showed that the impact of accidental eccentricity on the buckling strength of concentric braces varies according to the slenderness ratio. According to both experimental and numerical studies, the influence of accidental eccentricity becomes insignificant when the normalized slenderness ratio exceeds 1.5. However, when the normalized slenderness ratio is below 1.5, the effect of eccentricity becomes significant, and it increases in importance as the slenderness ratio decreases.