Testing of Full-Size Reinforced Concrete Beams Strengthened With FRP Composites: Experimental Results and Design Methods Verification

Abstract

In 1997, a load rating of an historic reinforced concrete bridge in Oregon, Horsetail Creek Bridge, indicated substandard shear and moment capacities of the beams. As a result, the bridge was strengthened with fiber reinforced polymer composites as a means of increasing load-carrying capacity while maintaining the historic appearance. Because composites were a relatively new construction material in infrastructure projects, subsequent tests were conducted to verify the design used on the bridge. Four full-size beams were constructed to match the dimensions and strength capacity of the bridge crossbeams as closely as possible. One of these beams was used as the control, while the other three beams were strengthened with various composite configurations including the same configuration used on the bridge crossbeams. The beams were loaded in third point bending to determine their capacity. The beam strengthened with the same composite design used on the bridge could not be broken with loading equipment used. Based on the maximum loads applied, the bridge beams have at least a 50% increase in shear and a 99% increase in moment capacity over the unstrengthened condition. Design calculations show the bridge beams now exceed the required shear and moment capacities.