Evaluation of a Timber Bridge for the Secondary Road System Using FRP Reinforced Glued-Laminated Girders

One of the goals that the Innovative Bridge Research and Construction (IRBC) program, sponsored by the Federal Highway Administration (FHWA), wishes to achieve through sponsored research projects is the concept of an economical, durable, short-span bridge that reduces construction time. Delaware County, Iowa took a step in that direction through the construction of a 64 ft. long bridge comprised of fiberreinforced polymer (FRP) reinforced glued-laminated timber girders and a transverse glued-laminated timber deck. Prior funding for the design, construction (including materials), and monitoring/evaluation of this project was obtained through the IBRC program with the assistance of the Iowa Division of the FHWA. Although strengthening of timber bridges with FRP is not a new topic, limited information exists on the shortand long-term effectiveness of using FRP reinforcement for these types of structures. Thus, the objective of this project was to evaluate the in-service structural performance of a glued-laminated timber bridge strengthened with FRP plates. Field load tests and inspections were performed immediately after construction and each year for two years after construction of the bridge. The purpose was to establish a database of information to address both shortand long-term performance using FRP plates to reinforce glued-laminated timber girders. Structurally, the bridge performed within current specified limits, and no significant increase in stiffness was identified in the girders due to the presence of the FRP plates. Test results collected in 2006 show no noticeable difference compared to those collected two years earlier in 2004, and the FRP/timber bond showed no signs of deterioration. Cost still appears to be the limiting factor for this bridge design, although, as this design gains familiarity, that cost may decrease, making it a more attractive alternative.