Seismic performance of circular RC columns subjected to axial force, bending, and torsion with low and moderate shear

Test results of reinforced concrete (RC) circular columns under cyclic bending and shear, cyclic pure torsion, and various levels of combined cyclic bending, shear, and torsion complimented with finite element (FE) results are presented in this paper. The main variables considered in this study are the ratio of torsion-to-bending moment (T/M)(T/M), and the aspect ratio (H/D)(H/D) of the column or bending moment to shear (M/V)(M/V) (to simulate low or moderate shear). The aspect ratio of the column determines the level of flexure–shear interaction. Under combined loadings, the columns were tested at torsion-to-bending moment ratios of 0.2 and 0.4 with aspect (H/D)(H/D) ratios of 6 and 3. This work analyzed the effect of an increase in aspect ratio with respect to several behaviors. Specifically, the significance of the level of shear on the failure modes and its effect on the torsional and bending strength under combined loadings is investigated. Test results demonstrate that there was no appreciable change in flexural or torsional capacities with decrease in aspect ratio as was observed in the FE analysis. However, results show a significant change in the failure mode and deformation characteristics due to reduction in aspect ratio.