Semiparametric Hazard Rate Models of Reinforced Concrete Bridge Deck Deterioration

Abstract

The development of models to predict the distribution of times between changes in condition-state for reinforced concrete bridge decks is presented in this paper. The authors used semiparametric hazard rate modeling techniques to develop stochastic duration models for bridge decks in the Indiana Bridge Inventory database. The advantage of semiparametric methods is that they do not constrain the hazard rate to follow a prespecified probability density function. This approach is flexible enough to accommodate different types of deterioration processes, and can account properly for both censored and uncensored data. Furthermore, it relates observed deterioration to relevant explanatory variables. Finally, because this approach quantifies the time-dependent hazard rate function, it facilitates the computation of time-dependent transition probabilities for use in bridge management systems. The models presented in this paper are characterized by realistic trends. The estimated parameters are statistically significant and have, for the most part, intuitively correct signs. However, the models include only a small number of explanatory variables, and thus do not capture the entire array of relevant factors that contribute to bridge deck deterioration. This is especially true when they are compared to the state-based models obtained in earlier research using the same data. The reasons are that the deck conditions are observed at infrequent points in time (every 2 years) and that the window of observation is relatively short (10 years).