Experimental evaluation of bar slip and strain penetration in reinforced concrete columns

Abstract

An experimental study on the effects strain penetration on the lateral performance of reinforced concrete columns is presented. Two cantilever columns with a diameter of 610 mm and an aspect ratio of 5.5 were tested under quasi-static cyclic loading. The specimens were nominally identical except for the anchorage of the column longitudinal steel in the adjacent footing. The first column had straight bar anchorages, while the second column had headed bars which were partially debonded along the footing to increase the effects of strain penetration and alleviate tensile strains in vertical steel. Optical deformation techniques were employed to monitor bar slip and base rotations during testing. Both columns presented a ductile response and failed by rupture of the vertical bars. The base rotation in the column with fully-bonded straight bars accounted for 25% to 35% of the total drift. In the column with partially-debonded headed bars, bar slip at the base of the column was more than doubled and base rotations accounted for 40% to 60% of the total drift. Partial debonding also resulted in more limited concrete damage and a larger deformation capacity. Experimental observations are complemented with nonlinear finite element analysis of the tests.

Postprint (published version)