Correlation between the inspection manual severity codes and moment coefficient for deteriorated concrete beams

Bridges form a vital part of any countries transport network. Roads users expect that these structures remain safely in-service day after day to enable travelers to complete their intended road journey without disruption. Concrete bridges in particular suffer deterioration due to the harsh environment that they are subjected to such as chloride attack from de-icing salts or carbonation attack due to the atmosphere. Inspection is, therefore, required to ensure that these structures are fit for purpose and safe to use. The UK Bridges Board has developed a comprehensive Inspection Manual to ensure all structures are uniformly inspected and to a high standard. The inspection process involves completing a proforma where defects are graded between 1 (no defect) to 5 (collapse). The inspector is able to use a table (Table G. 10) within the Inspection manual, which provides guidance on severity descriptions for different construction materials. However, for reinforced concrete beams exhibiting main steel corrosion, the relationship between severity of defect and loss of strength is not quantitatively obvious. The paper gives the bridge inspector an appreciation of the loss of strength as a result of corrosion to reinforced concrete simply supported beams. The analysis is mainly concerned with the predicted loss at severity code 3 from the manual, which assumes moderate defect/damage, with some loss of functionality.