Experimental Study and Residual Performance Evaluation of Corroded High-Tensile Steel Wires

摘要

To evaluate the residual service performance of corroded high-tensile steel wires, a batch of in situ wires that had served for 13 years in the hangers of an arch bridge was investigated. Four types of corroded wires were derived from the in situ wires by placing them in the indoor environment for 1.5 years (Type A) or treating them in an alternate dry-wet environment for 0.25-1.5 years (Types B, C, and D). The mechanical properties of the corroded wires were investigated with tensile and fatigue tests, and the fracture characteristics were observed. Fatigue tests on Type A wires with different stress ranges were conducted, and the stress intensity factor range Delta K-p at the bottom of crack-initiation pits was analyzed. According to the S-N curve for Type A wires, the crack-propagation characteristics of steel wires were investigated. The linear elastic fracture mechanics (LEFM) approach was used to predict the residual life of corroded wires in two systems of arch bridges. The tests show that the ultimate strain of corroded wires decreased with an increase in degree of corrosion. The fatigue properties of wires were found to degrade significantly at the early corrosion stage, and the degradation rate slowed down with further development of corrosion. The correlation between the fatigue life and the stress intensity factor range DKp at the bottom of corrosion pits shows that larger pitting size tended to have shorter life under the same stress range, and fatigue cracks were difficult to initiate at the corrosion pits below the fatigue threshold. The crack-growth parameters of the Paris law identified from the S-N curve of Type A wires were m = 2.87, C = 8 x 10(-12) under the stress ratio R = 0.5. The residual life predicted by LEFM shows that in a dry environment, corroded wires with an initial pitting depth of 0.6 mm can serve for more than 30 years in arch-beam combination-system bridges, whereas they can only serve for 5 years in floating-system arch bridges.