Experimental and numerical investigations on the size effect of moderate high-strength reinforced concrete columns under small-eccentric compression

The paper deals with an experimental investigation and numerical simulation of moderate high-strength reinforced concrete (RC) columns subjected to a small-eccentric compressive loading (e₀ = 0.25h₀). A series of tests on the behavior of 12 geometrically similar moderate high-strength reinforced concrete columns with two different stirrups ratios (i.e., 0% and 0.66%) were conducted. The maximum structural size of the square reinforced concrete columns was 800 mm. A 2D mesoscale method for the simulation of the behavior of reinforced concrete columns was established. The numerical tests on the reinforced concrete columns with larger stirrup ratios (1.2% and 2.4%) were carried out complementarily, based on the fact that the simulation results were consistent with the available test observations. The failure patterns, the nominal compressive stress–strain relationships, the nominal compressive strength, and the post-peak softening behavior of the reinforced concrete columns were studied. Furthermore, the influence of stirrups on failure behavior and size effect of the reinforced concrete columns was revealed. One can conclude that (1) the size effect exists in the nominal compressive strength of the eccentrically loaded high-strength reinforced concrete columns with the four different stirrup ratios; (2) comparison of the present test results and the “size effect law” proposed by Bažant shows good agreement; (3) the presence of stirrups improves the nominal strengths, makes the failure of columns less brittle, and weakens the size effect; and (4) the proposed mesoscale numerical method is capable of describing the mechanical behavior of eccentrically loaded reinforced concrete columns.