International Journal of Transport, Highways & Railways Engineering
Author(s) : NIROSHAN K. WALGAMA WELLALAGE , RICHARD DWIGHT, TIELING ZHANG
State-based Markov deterioration models (SMDM) sometimes fail to find accurate transition probability matrix (TPM) values, and hence lead to invalid future condition prediction or incorrect average deterioration rates mainly due to drawbacks of existing nonlinear optimization-based algorithms and/or subjective function types used for regression analysis. Furthermore, a set of separate functions for each condition state with age cannot be easily derived by using Markov model for a given bridge element group, which however is of interest to industrial partners. This paper presents a new approach for deterioration modelling that follows homogeneous Markov models, namely, the Modified Weibull approach, which consists of a set of appropriate functions to describe the percentage condition prediction of bridge elements in each state. These functions are combined with Bayesian approach and Metropolis Hasting Algorithm (MHA) based Markov Chain Monte Carlo (MCMC) simulation technique for quantifying the uncertainty in model parameter estimates. In this study, the inspection data for 1,000 Australian railway bridges over 15 years were reviewed and filtered accordingly based on the real operational experience. Network level deterioration model for a typical bridge element group was developed using the proposed Modified Weibull approach. The condition state predictions obtained from this method were validated using statistical hypothesis tests with a test data set. Results show that the proposed model is not only able to predict the conditions in network-level accurately but also capture the model uncertainties with given confidence interval.