Four full-scale reinforced concrete beams were replicated from an existing bridge. The original beams were substantially de®cient in shear strength, particularly for projected increase of traf®c loads. Of the four replicate beams, one served as a control and the remaining three were implemented with varying con®gurations of carbon ®ber reinforced polymers (CFRP) and glass FRP (GFRP) composites to simulate the retro®t of the existing structure. CFRP unidirectional sheets were placed to increase ¯exural capacity and GFRP unidirectional sheets were utilized to mitigate shear failure. Four-point bending tests were conducted. Load, de¯ection and strain data were collected. Fiber optic gauges were utilized in high ¯exural and shear regions and conventional resistive gauges were placed in eighteen locations to provide behavioral understanding of the composite material strengthening. Fiber optic readings were compared to conventional gauges.
Results from this study show that the use of ®ber reinforced polymers (FRP) composites for structural strengthening provides signi®cant static capacity increases approximately 150% when compared to unstrengthened sections. Load at ®rst crack and post cracking stiffness of all beams was increased primarily due to ¯exural CFRP. Test results suggest that beams retro®t with both the designed GFRP and CFRP should well exceed the static demand of 658 kN m sustaining up to 868 kN m applied moment. The addition of GFRP alone for shear was suf®cient to offset the lack of steel stirrups and allow conventional RC beam failure by yielding of the tension steel. This allowed ultimate de¯ections to be 200% higher than the pre-existing shear de®cient beam. If bridge beams were retro®t with only the designed CFRP failure would still result from diagonal tension cracks, albeit at a 31% greater load. Beams retro®t with only the designed shear GFRP would fail in ¯exure at the mid-span at an equivalent 31% gain over the control specimen, failing mechanism in this case being yielding of the tension steel. Successful monitoring of strain using ®ber optics was achieved. However, careful planning tempered by engineering judgement is necessary as the location and gauge length of the ®ber optic gauge will determine the usefulness of the collected data.