Experimental research on high strength concrete slender columns subjected to compression and uniaxial bending with unequal eccentricities at the ends

This paper presents an experimental research on 32 columns tested with unequal eccentricities at the ends. The purpose of this research is twofold: first, the contribution to the knowledge of these components and second, to calibrate and check simplified approaches. The analyzed variables are: the concrete strength (normal and high strength), the slenderness, the amount of longitudinal reinforcement, the ratio between eccentricities at the ends and the relative eccentricity applied. Ultimate strength and deformed shape of the column have been analyzed and simplified approaches proposed by EC-2 (2004) and by ACI-318 (2008) have been compared with experimental results. In general, the accuracy of the simplified methods proposed in the EC-2 (2004) and the ACI-318 (08), for HSC columns is lower than for NSC columns.Ductility factor (μΔ) according to (EC-8 (2005)) has been assessed among the experimental tests in order to compare the displacement capacity. In general, ductility increases when the relative eccentricity (e2/b), the ratio between eccentricities (β), and the amount of longitudinal reinforcement (ρl) increase, and when the slenderness of the column (λg) and the concrete strength (fc) decreases.

► Results of 32 experimental tests on high strength concrete slender columns.
► A new system to applied loads with unequal eccentricities at the ends of columns is described.
► Ductility increases if the eccentricity and the amount of reinforcement increases.
► Ductility increases if the ratio between eccentricities increase.
► Ductility increases whether the slenderness and the concrete strength decreases.