AN EXPERIMENTAL STUDY ON SCALE EFFECTS IN SHEAR FAILURE OF REINFORCED CONCRETE COLUMNS

A shear dominated full-scale rectangular reinforced concrete column was tested under cyclic lateral loading. Two 1/2-scale units and three 1/4-scale units were designed to model the full-scale column as accurately as possible and tested using the same loading pattern as the full-scale column. Test variables also included the maximum aggregate size that was consistently scaled in accordance with the column size. The purpose of the test was to investigate the effect of scale on the shear behavior of reinforced concrete columns. The overall behaviors of the small-scale units were quite similar to the full-scale specimen during testing. The flexural and shear deformation components seemed to be consistently scaled and no scale effect was found. However, the shear crack inclination and the maximum crack width at an equivalent loading stage were different, which gave rise to the difference of the activation and the increasing rate of the transverse steel shear-resisting mechanisms Vs and consequently the difference of the degradation of the concrete shear-resisting mechanisms Vc. The concrete shear contribution computed from the applied lateral load and the measured hoop strains showed the scale effect in its maximum value for the test units with both constant and proportional aggregate size. On the other hand, though the Vc component at the maximum column strength decreased as the column size increased when the constant aggregate size was applied, no size effect was observed for the test units with proportional aggregate size. Design equations incorporating a scale factor seemed to appropriately estimate the concrete shear contribution, while that without size effect might be unconservative for large size columns