Long-term experimental study and prediction of the mechanical performance on corroded prestressing steel strands subjected to marine salt spray environment

Steel strands subjected to marine salt spray environments are prone to corrosion, which can lead to degradation of their mechanical properties and ultimately affecting the safety of prestressed structures in service. Therefore, one of the most urgent scientific issues for prestressed structures is the assessment of the deterioration caused by long-term corrosion in steel strands. In this study, based on the environmental conditions of a specific coastal area, a similar neutral salt spray environment is simulated in an artificial climate chamber to analyze its influence on the mechanical behavior of prestressing strands. Long-term corrosion experiments on prestressing strands are conducted over a period of 10 months. Different corrosion periods, corrosion environments, and stress levels are considered to assess the prestressing force loss of strands in marine salt spray environments. The test results indicate that prestressing force loss increases with the growth in corrosion duration under combined stress and corrosion. Furthermore, the prestressing force of the strands enters an accelerated stage of plastic degradation after 9–10% corrosion loss. After the long-term corrosion test is completed, tensile tests are conducted on the strands to study the effect of corrosion on the tensile mechanical properties of strands. The results show that the ultimate strength of the corroded strands decreases as the corrosion loss increases. When the corrosion loss exceeds 17%, the strands in the tensile process directly exhibit brittle fracture without experiencing ductile development stage. Subsequently, a novel time-dependent model is proposed to predict the prestressing force loss caused by the corrosion in strands, and a finite element model is established to analyze the tensile mechanical properties of corroded strands. Finally, the experimental results are employed to validate the two proposed models. The results demonstrate that the proposed models can reasonably predict the prestressing force and constitutive relationship of prestressing steel strands.