Ideal buckling strength of compression angle members considering the bending stiffness of horizontal members

초록

Angle-section chords in lattice structures exhibit complex stability behavior due to their open, monosymmetric geometry. Current design standards lack a practical method for directly quantifying the increase in buckling load capacity provided by horizontal braces based on their bending stiffness, often containing simplified effective length factors. To address this gap, a parametric study of 342 finite element chord-brace assembly models was conducted to investigate the effect of brace stiffness on the critical buckling load of slender angle chords with nonslender sections using single- and double-bolt configurations. A geometric nonlinear arc-length analysis was used to determine the critical buckling loads (Pcr) while accounting for bolt pretension and contact nonlinearities. The results consistently indicated that the governing failure mode was global flexural buckling about the minor principal axis of the chord. The brace stiffness provided significant rotational restraint; for 2-bolt connections, the effective length factor (K) was reduced from the pinned value of 1.0 to as low as 0.654, yielding up to a 133.5% increase in buckling capacity relative to the unbraced column. Based on these findings, a closed-form multiplier, developed using nonlinear regression, is proposed to accurately predict this enhanced buckling capacity as a function of the brace-to-chord bending stiffness ratio (rho) and chord slenderness (lambda). This multiplier provides a practical design tool that enables a more accurate and economical design of latticed steel structures than the simplified methods currently available in design specifications.

키워드