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This paper describes an experimental program designed and executed to investigate the failure mode and ultimate capacity of web-reinforced pultruded FRP beams subjected to concentrated loads in the plane of the web. Six 203.2 mm × 101.6 mm × 12.7 mm beams and five 203.2 mm × 203.2 mm × 9.5 mm beams manufactured with vinylester resin were strengthened with one of three systems and subjected to concentrated loads applied directly to the top flange. The three systems were (a) full-depth web bearing stiffeners, (b) “doubler” plates attached to the web, or (c) stiffening elements applied to the upper (loaded) web-flange junction of the specimen. Experimental results showed that the junction stiffeners (58.7%), bearing stiffeners (52.8%), and “doubler” plates (31.7%) all increased the ultimate capacity of the beams when compared to unstrengthened control beams. Beams prepared with bearing stiffeners and “doubler” plates failed in the same manner as the control beams (shear “wedge” failure at loaded web-flange junction), while failure in the beams with reinforced loaded web-flange junctions occurred in the bottom flange near the simple supports. Digital image correlation software was used to capture out of plane displacement of the web and confirms the modes of failure.

Results of the behavior of pultruded fiber-reinforced polymer (FRP) I-shaped beams subjected to concentrated loads in the plane of the web are presented. Twenty beams with nominal depths from 152.4 to 304.8 mm were tested in three-point bending with a span-to-depth ratio of four. Load was applied to the top flange directly above the web—12 without bearing plates and 8 with bearing plates of varying width and thickness. All test specimens failed with a wedgelike shear failure at the upper web-flange junction. Finite-element results support experimental findings from strain gauge and digital image correlation data. Bearing plates increased beam capacity by 35% or more as a function of bearing plate width and thickness. Bearing plates increased average shear stress in the web at failure from 17.4 to 27.2 MPa—below the accepted value of in-plane shear strength (69 MPa). A design equation is presented, and predicted capacities are compared with experimental results. The average value of experimental capacity t...

A new method has been developed for strengthening reinforced concrete beams for flexure which uses multiple mechanical fasteners to attach a fiber reinforced polymer (FRP) strip to the member. This study investigates the behavior of the method on full scale concrete T beams of three different steel reinforcement levels. The beams were strengthened without surface preparation, and the strips were attached with only four man-hours of labor per beam. The strengthened beams resulted in increases of up to 11.7 % in the yield moment and up to 27.2 % in the moment capacity at a deflection of L/135. The beams exhibited large amounts of ductility, before failure.

Five 609.5-mm deep fiber-reinforced polymer (FRP) beams with a span-to-depth ratio of 4∶1 were tested in three-point bending with the beam ends constrained to prevent global failure. A concentrated load was applied at midspan either directly to the top flange or through a 101.6 mm wide by 12.7-mm thick FRP bearing plate resting on the top flange. VIC-3D Digital Image Correlation Measurement Software from Correlated Solutions captured out-of-plane displacement of the webs, and Southwell plots were generated to determine buckling loads. Each specimen experienced a stability failure of the web before undergoing material failure in the upper web-flange junction. On average, web buckling occurred at 90% of the ultimate load. The introduction of a bearing plate did not significantly affect the buckling load or ultimate capacity of the specimens. One specimen was tested into the postbuckling range, unloaded, and reloaded to material failure and experienced no loss of strength or stiffness. Another specim...