Constitutive model for ultra-high performance concrete (UHPC) considering the size effect under cyclic compressive loading

In this study, the size effect of the thickness of the specimen on the mechanical properties of UHPC was investigated through compression tests under cyclic loading. UHPC prisms with different thicknesses from 20 mm to 100 mm were tested under unloading/reloading cycles and the stress-strain curves were recorded for this purpose. A constitutive model to predict the stress-strain response of UHPC accounting for the thickness was proposed. It was found that UHPC specimens with different thicknesses showed the same failure mode of di-agonal shear failure. The size effect of thickness was significant for the compressive strength but was negligible for the peak strain and elastic modulus. The damage of the unloading modulus and reloading modulus at zero stress only occurred when the unloading strain exceeded 0.8 times the peak strain. Furthermore, the proposed constitutive model could predict the stress-strain response for UHPC with different thicknesses under cyclic compressive loading with acceptable accuracy.

Automated summary

The size effect of specimen thickness on the mechanical properties of UHPC was investigated through cyclic compression tests. UHPC prisms with thicknesses ranging from 20 mm to 100 mm were tested and a constitutive model accounting for the thickness was proposed. It was found that different thicknesses of UHPC specimens exhibited the same diagonal shear failure mode. The compressive strength was significantly influenced by the thickness, while the peak strain and elastic modulus showed negligible size effects. Damage in the unloading and reloading modulus at zero stress occurred only when the unloading strain exceeded 0.8 times the peak strain. The proposed constitutive model accurately predicted the stress-strain response of UHPC with different thicknesses under cyclic compressive loading.