Biaxial compression behavior of concrete under repeated loading

The primary objective of this study was to investigate the behavior of concrete subjected to repeated biaxial compressive loading. Square plate specimens of concrete were tested under in-plane repeated loading that included two different unloading schemes (complete unloading to zero and partial unloading to 0.2f(c) stress level) and five stress ratios (alpha = 0, 0.25, 0.5, 0.75, and 1.0). The stress-strain curves of the specimens in each test series were measured and presented here. The regular patterns of strength, strains at the peak stress, residual strains, envelope of stress-strain curves, locus of common points, and unloading and reloading curves are analyzed. An analytical model that predicts the loading, unloading, and reloading curves of concrete subjected to repeated biaxial compressive loading with complete and partial unloading is proposed. The deformation characteristics of concrete under repeated biaxial compressive loading are compared with those under monotonic biaxial compressive loading and repeated uniaxial compressive loading.