Deterioration Prediction Modelling and Inspection Schedule Estimation for Concrete Bridge Decks

Accurate and reliable deterioration rate estimates for concrete bridge decks are an important part of the overall bridge condition assessment. The main objective of this paper is to determine the time in condition ratings (TICRs) of concrete bridge decks and assess the impact of average daily traffic (ADT), age, and deck area on the bridge deck condition. Condition ratings of bridge decks over 24 years for Michigan state were collected from the National Bridge Inventory (NBI) data. The Anderson-Darling statistical test was used to evaluate and rank five practical probability distribution functions to select the best fit for Michigan state data. The results indicate that the best statistical model for Michigan state data is the lognormal function. It was illustrated that the TICR decreases when the condition rating decreases. When a concrete bridge deck condition is rated at 8, it can take 11.29 years to drop to the lower rating of 7. However, when the concrete bridge deck condition is rated at 4, it may take 6.64 years to drop to the lower condition rating of 3. It was also observed that on average, bridge decks in Michigan stay much longer than the typical inspection interval (i.e., 2 years), suggesting that inspection intervals can be longer than 2 years for bridges in good condition ranges. The results also show that ADT, age, and deck area are important factors in the deterioration rates of concrete bridge decks.