The AIJ "Recommendations for the Design and Fabrication of Tubular Structures in Steel" specifies that the effective length lk of a compression chord for the out-of-plane buckling of a steel tubular truss could be shorter than the distance between the lateral supports, since the compression chord is laterally stiffened by the tension chord and the web members. In terms of increasing the buckling strength of the truss, it might be economical to enlarge the cross section of the compression chord only. However, the effective length of the chord should be somewhat longer than lk, so that the tension chord, which section must become relatively small, would lose a bit of the stiffening effect for the compression chord. The paper will present the method to evaluate the effective length of the compression chord for that.
