Damage constitutive model of concrete under repeated load after seawater freeze-thaw cycles

Offshore concrete structures in cold climates inevitably experience seawater freeze-thaw cycles, which increase surface scaling and internally damage the concrete, thereby altering the mechanical properties. The constitutive relation and compression damage to the concrete after seawater freeze-thaw cycles are absent from existing studies of structural nonlinearity. Repeated uniaxial compression tests on prism specimens were conducted to investigate the stress-strain and the damage variable of the concrete after 0, 25, 50, 75, 100, and 125 seawater freeze-thaw cycles. Using plastic damage theory and experimental results, we developed a constitutive model of concrete subjected to seawater freeze-thaw cycles, which was input to ABAQUS for numerical simulation. The results showed that the reloading stiffness degradation trend of compression was basically the same for different numbers of freeze-thaw cycles. Compression damage could be calculated by uniform equations after the peak point. The modeling results matched well with the experimental results, indicating that the constitutive model can provide a theoretical basis for nonlinear analysis or design of offshore bridges in cold climates.