Modelling of bridge elements deterioration for Serbian bridge inventory

Abstract

In order to improve bridge management practice for public roads in Serbia, a deterioration model for bridge elements was developed using condition data collected over the last 20 years. The distribution of condition data over condition states allows the estimation of reasonably reliable deterioration models even for advanced deterioration. Based on the literature review, discrete-time Markov chains were chosen for this purpose. Estimating the transition probabilities of discrete Markov chains is straightforward when the time between condition records on bridge elements closely matches the chosen time interval for the Markov chain, which is not the case with condition data in Serbia. To overcome this problem, an expectation maximisation (EM) algorithm has been applied to estimate the transition probabilities. It is shown here that the EM algorithm is a sound and robust method, which can yield a reasonable deterioration model even if limited data are available. In addition, the EM is used to determine the overall bridge deterioration using existing agency rules to derive bridge rating from element condition states.