Pitting Damage Characteristics on Prestressing Steel Strands by Combined Action of Fatigue Load and Chloride Corrosion

Prestressing steel bars are damaged in the typical pattern of corrosion fatigue under the combined action of chloride corrosion and fatigue load, in which the two damage types are mutually promoting. This study experimentally investigates the promotion effect of fatigue on corrosion. Twelve prestressed concrete beam specimens with steel strands that bore the combined action of corrosion and fatigue for 20 days were prepared using four chloride concentrations and three fatigue stress ranges. Moreover, the specimens were subsequently broken to measure the size of the corrosion pits. Based on these measured sizes, the volume and stress intensification factor (SIF) of the pits were calculated and their volumes and SIFs were statistically analyzed. The results show that the steel strands corroded in the typical pitting corrosion pattern with approximately anticlastic or spheroid shapes. The parameters of the pit's volume and SIF showed both normal and lognormal distributions. Thus, it was observed that the greater the action intensity of fatigue, the larger were the averages of the two parameters and the 95th fractile of the lognormal distribution of the SIF. (C) 2017 American Society of Civil Engineers.