Experimental tests of slender reinforced concrete columns under combined axial load and lateral force

The use of high strength concrete (HSC) in columns has become more frequent since a substantial reduction of the cross-section is obtained, meaning that slenderness increases for the same axial load and length, producing higher second order effects. However, the experimental tests in the literature of reinforced concrete columns subjected to axial load and lateral force focus on shear span ratios, according to Eurocode 2 (2004), clause 5.6.3., (M/(V⋅h))(M/(V⋅h)) lower than 6.5. This gap in the literature limits technological development for the construction of these structural elements. This paper presents 44 experimental tests on reinforced concrete columns subjected to constant axial load and monotonic lateral force. The aim of this is to gain greater knowledge of the types of elements which will also be of use in calibrating the numerical models and validating the simplified methods. The test parameters are strength of concrete (normal- and high-strength concrete), shear span ratio, axial load level and longitudinal and transversal reinforcement ratios. The strength and deformation of the columns were studied, and an analysis of the simplified methods from Eurocode 2 (2004) and ACI-318 (2008) concluded that both are very conservative.

► Spalling of concrete cover is produced for lower axial load levels and HSC.
► A criterion to identify the failure mode was defined from total bending moments.
► The potential length of the plastic hinge depends on the type of failure.
► The ductility in displacements decreases with confinement, shear-span ratio and fcfc.
► The Eurocode-2 and ACI-318 are safe for both criteria of failure.