ABSTRACT
Timber bridges are used extensively on secondary roads in the U.S. and account for nearly 10 percent of the half-a-million bridges in the National Bridge Inventory (NBI) database. Since the NBI database considers only bridges with timber in the superstructure as a timber bridge, the overall number of bridges that utilize timber in the super- or sub-structure is significantly higher than 10 percent. Timber bridges are popular because of the ease of construction, lower construction costs and not needing specialty contractors or heavy equipment. A vast majority of the timber bridges have been in service for 30–60 years and nearly half of all these timber bridges are structurally deficient or functionally obsolete. The primary reason for this high level of deficiency in these bridges is the failure to incorporate construction details and practices that inhibit the adverse impacts of the environment and biological infestation. The service life of a properly constructed timber bridge is comparable or better than that of a concrete or steel bridge. This paper presents an overview of a study undertaken by the author to assess the condition of timber bridges in the Southeastern United States and identify the factors that are adversely impacting their durability, performance and load rating. Load posting of these timber bridges causes havoc for the rural communities that are dependent of this transportation lifeline. Giving a severely strained transportation funding program, replacing the numerous deteriorated timber bridges is neither affordable nor viable. The current scenario offers an excellent opportunity to deploy FRP composites in the repair and rehabilitation of deteriorated timber bridges to restore their load rating and avoid the prohibitive cost of replacing these bridges. The effective FRP repair and rehabilitation methods are discussed and examples of presented. The challenges associated with using FRP for timber bridge repair are discussed and recommendations are made for restoring/enhancing the load rating of the bridges.
