Effect of web reinforcement on the behavior of pultruded fiber-reinforced polymer beams subjected to concentrated loads

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.