The lateral buckling strength of chords in tubular trusses is frequently much higher than the buckling strength evaluated on the assumption that the effective length is equal to the distance between lateral supports. Reasons for this include restraints supplied by web members, nonuniform distributions of axial force over the laterally unsupported length of the chord, and a decline of tangent modulus in the member under the greatest axial force when the chord buckles in the inelastic region. This paper proposes a new design method that takes these effects into consideration and shows how the results according to the proposed method agree well with those obtained from exact solutions based on a nonlinear buckling analysis.
