PLASTIC ROTATION AND LOAD CARRYING CAPACITIES OF H-SHAPED STEEL BEAMS WITH LATERAL AND LOCAL BUCKLINGS UNDER UNEQUAL-END MOMENTS

The wide-flange steel beams were tested under unequal-end moments, in order to clarify the effects of bending moment gradient on the plastic rotation and maximum load carrying capacities of a beam. End moment ratio ρ (=M_2/M_1, M_2, M_1= bending moment at the ends of a specimen, |M_2|＜|M_1|) and lateral slenderness ratio ℓ_b/j_y (ℓ_b=laterally unbraced length, j_y=radius of gyration of a cross section about weak axis) were selected for the experimental variables. The test program concists of three series. For two of them with the value of ρ equal to 0 or -0.4, the values of ℓ_b/j_y are 45, 60, 75, 90 and 105. For another with the value of ρ equal to -0.8, the values of ℓ_b/j_y are 45, 75, and 105. Based on the experimental results, the applicability of the empirical formulas about plastic rotation capacities of beams (Ref.12) were discussed. Furthermore the experimental maximum load carrying capacities were compared with allowable bending moment based on Ref.14. The results may be summarized as follows : 1. The empirical formulas reported in Ref.l2 can be applied to the region of ρ≤0, and experimental values (R_exp) and predicted values (R_pred) of plastic rotation satisfy the following equations....[the rest omitted