Performance of Aging Timber Bridges based on Field Tests and Deterioration Models

This study investigated the performance of timber trestle railroad bridges through field tests on aging open- and ballast-deck bridges. It also developed nonparametric deterioration models based on average time in condition rating (ATICR) and Kaplan-Meier (K-M) estimates to assess the performance of timber highway bridge components using National Bridge Inventory data. This study proposes ATICR-based deterioration models for predicting the condition of timber bridge components. Average service life of highway timber multibeam bridge components under routine maintenance without any reconstruction or rehabilitation was found to be 23 years for the decks, 26 years for the superstructures, and 27 years for the substructures. K-M estimate-based reliability models were developed for probabilistic prediction of bridge safety while accounting for partial information from incomplete bridge condition observations. Based on these models, the median survival year-the number of years for which 50% of the bridge population remains in its current condition without deterioration-was obtained as 10 years for the decks, 14 years for the superstructures, and 12 years for the substructures of timber multibeam bridges. The models also suggested there was an 80% chance the timber bridge components would remain in their current condition without deterioration to a lower condition for a minimum of 3 years. The analysis carried out in this study could help improve the management and maintenance of timber bridges that are currently in operation worldwide.