Effect of size on the response of cylindrical concrete samples under cyclic loading

•Effect of size on the cyclic response of cylindrical concrete samples is considered.•Samples of different diameter and aspect ratio are tested under cyclic loading.•Cyclic parameters are shown to be influenced by the diameter and aspect ratio.•At smaller diameters, the post-peak response is less affected by the aspect ratio.•Different cyclic-damage indices are used to describe the cyclic parameters. An experimental program is carried out to investigate the relation between size and the cyclic response of cylindrical concrete samples. For this purpose, normal strength concrete samples are cast in 9 different sizes and tested under strain-controlled cyclic loads. With the 9 sizes forming an array of samples with different diameters and aspect ratios, the effect of size on peak stress and peak strain is determined. Normalized cyclic stress–strain curves are then used to evaluate the variation of cyclic parameters in terms of the diameter and aspect ratio of the sample. The results of this study show that the diameter and the aspect ratio of the sample have the most influence on the reloading strength and reloading tangent of the cyclic response. Moreover, a key feature deduced from the results is that as the diameter of a sample becomes smaller, the effect of aspect ratio on the post-peak response diminishes. Finally, cyclic parameters are plotted against three different definitions of the damage index. With these definitions being based on strain, strength and dissipated energy, the results imply that the degradation of different cyclic properties might be originating from different damage mechanics.