Abstract:
Recent deterioration of pretensioned concrete bridge beams in New Zealand and Australia highlights an escalating problem. Pretensioned reinforcement corrosion is especially critical because of the highly stressed nature of the structures. Only a small amount of corrosion is required to a pretensioned strand before a considerable reduction of the structural capacity of the member occurs. The Tiwai Point Bridge is located in a highly aggressive environment near Invercargill in the South Island of New Zealand. It consists of twenty seven 60 ft (18 m) spans; each span consists of nine 2‘3“ (686 mm) deep tee beams which contain both pretensioned and posttensioned reinforcement. The bridge was opened in 1969 and since that time chloride ingress has resulted in severe corrosion of the pretensioned reinforcement. Each beam was subjected to a number of non-destructive corrosion assessment procedures. These results were used to estimate the ultimate strength of each beam. Each beam was then loaded to failure on a custom built four point flexural testing rig. The worst condition beams had damage to all four strands in the bottom layer and achieved strengths of 68% and 69% of their good condition counterparts. The aim of this research was to assess the residual strength of beams which had experienced pretensioned reinforcement corrosion. The progression of corrosion damage observed in the beams was described and a model was presented for assessment of the beams using nondestructive means. The measured strength of the corroded beams was compared to nominally identical beams which had not experienced corrosion.