Stability behavior of single-angle members with new double-leg connection

Single-leg connections are commonly used for angle members in lattice structures due to their constructability. However, this connection type results in significant eccentricity and compromises member stability. To optimize the load-transfer mechanism of angle members, this study proposes a novel double-leg connection method. Numerical simulations were conducted to preliminarily evaluate the proposed connection, leading to design parameter recommendations. Subsequent experimental investigations examined the compressive stability of double-leg connected angles, analyzing ultimate capacities and failure modes of both equal-leg and unequal-leg angles across various slenderness ratios. Specimens with low slenderness ratios primarily failed by local buckling, whereas those with high slenderness ratios exhibited flexural instability, with the bending axis significantly influenced by eccentricity and cross-sectional geometry. Experimental results demonstrated that the proposed connection improves the stability bearing capacity of angle steel members, with a maximum increase of 34%. Extended finite element analyses indicate that the normalized slenderness ratio effectively unifies the stability coefficient curves of members with different steel grades, whereas the curves of different cross-sections differ in the small-slenderness range due to the influence of local buckling and almost coincide at large slenderness ratios. Finally, the equivalent slenderness ratio formulas established separately for equal-leg and unequal-leg angles show good agreement with the test and finite element results, respectively, significantly outperforming the current design codes.