A study of the effects of corrosion on the deterioration of steel and concrete highway structures is currently underway. The study aims to provide a practical tool for use in the assessment of highway structures such that indications of future performance can be obtained for a number of different bridges. The methodology allows comparisons of the future repair and maintenance needs of a bridge stock to be made and thus aids in the decision making process of fund allocation. The project is funded by the Highways Agency in the UK.
Steel and concrete structures are both affected by corrosion. The main cause of corrosion in structures around the UK is the application of de-icing salts to roads. Chloride ingress results from leaking expansion joints and from vehicle spray.
Theoretical models exist for the prediction of corrosion in both concrete and steel structures. These can be used to predict the onset of corrosion and also the rate of corrosion loss. Once corrosion has initiated the effects of loss of cross-sectional area on the section capacity of a bridge element can be calculated.
The corrosion modelling has been applied in both deterministic and probabilistic analyses of bridges. The resultant has been a number of "whole life profiles" showing the effects on corrosion on the load capacity factor and the reliability index over a period of time. A sample whole life profile is shown below.
Dr Campbell Middleton
Dr Victoria Hogg