Mechanical behavior and size effect of moderate high-strength RC columns under monotonic and cyclic axial compression

•Size effect tests of 16 high-strength RC columns under axial compression are reported.•The cross-sectional size of the RC columns ranges from 200 mm to 800 mm.•Test results confirm the existence of size effect in relatively larger-sized RC columns.•The nominal strength of RC columns follows closely the size effect law proposed by Bažant.

The reliable design of reinforced concrete (RC) structures against external mechanical forces, including earthquake-induced, impact and other types of forces, necessitates a clear understanding of the mechanical behavior and size effect of moderate high-strength RC structural members under cyclic loading. This study presents the results of an experimental study on a series of geometrically similar moderate high-strength RC columns under monotonic and cyclic axial compression. A total of 16 moderate high-strength RC columns with different structural dimensions (in the ratio 1:2:3:4) were tested. The cross-sectional size of the columns was between 200 mm and 800 mm, and the length varied from 600 mm to 2400 mm. The overall mechanical performances of the moderate high-strength RC columns, including the failure patterns, the hysteretic curves, the nominal compressive stress-strain relationships, the peak load-carrying capacity, the energy-dissipation capacity, the nominal compressive strength, the concrete softening behavior and the buckling/necking of steel rebar were observed and explored. The test observations indicate the existence of size effect in relatively larger-sized moderate high-strength RC columns under both monotonic and cyclic axial compression, and the RC columns under cyclic loading pronounce a more obvious size effect. It is found that the bi-logarithmic plots of nominal compressive strengths for different moderate high-strength RC columns follows closely the “size effect law (SEL)” proposed by Bažant.