Torsionally Stiff Columns under Eccentric Loads

A computer program was developed to predict the strength of hollow rectangular tubular columns with ends pinned and free to rotate in any direction for various load eccentricities with respect to the strong axis. A key assumption in the theory used is that the rectangular section had enough torsional stiffness to make any twisting of the column negligible. This assumption and the theory in general were verified by testing eight 4-in. by 2-in. by 0.1875 in columns of A36 steel. It was concluded that the load reduction at the theoretical intersection length increases for smaller values of the ratio of weak to strong axis radius of gyration and for increasing values of the ratio of weak-to-strong axis radius of gyration and for increasing values of load eccentricity. The maximum reduction for a member with width-to-depth ratio 0.40 is about 9% when the load is applied to the edge of the member. The failure of unbraced column with bending about the strong axis will occur by lateral buckling except, possibly, in the case of very short members.