Load Testing and Rating of a PC Bridge Without Structural Plans

Located in Spencer County, Kentucky, USA, a 202.7 m (665 ft) 7-span prestressed concrete bridge carries KY-248 over Little Beech Creek. Constructed in 1981, this bridge has no available structural plans and has a gross load posting of 20 tons (22 US tons). This paper details the assumptions and methodology used to determine the safe live load capacity of the bridge utilizing diagnostic load testing. The load testing program and load rating were performed in accordance with the AASHTO Manual for Bridge Evaluation. This method involved the conservative assumption of the prestressing, development of a 2D Finite Element model, and adjustment of the model results based on field measured strain data. Despite a lack of structural plans, the rating methodology used allowed for a conservative confirmation that the bridge has sufficient capacity to support legal traffic without restriction.