An investigation into the behavior of fiber-reinforced polymer (FPR) beams subjected to concentrated loads in the plane of the web

Twenty-four tests were conducted on pultruded vinylester/glass beams from 6" to 12" deep with the concentrated load applied to the top flange. Specimens failed at upper web-flange junction in interlaminar shear. Failure took form of a "V"-shaped wedge driven into web accompanied by longitudinal cracking. Failure occurred at 0.14 to 0.32 the accepted value for in-plane shear strength. Finite element models supported results and verified interlaminar shear strength as controlling material property.;Thirteen tests were conducted on vinylester/glass specimens loaded through a bearing plate. Addition of bearing plates did not change failure mode. Increased cracking along the web-flange junction and more abrupt failures were observed. Plates increased capacity by 35% or more. Samples failed at 0.28 to 0.54 the accepted in-plane shear strength. Bearing plate width and thickness affected amount of capacity gained.;A closed-form design equation was developed to predict capacity with or without bearing plates. For beams without bearing plates, the ratio of experimental to predicted capacity was 1.07 with a coefficient of variance of 0.10. For beams loaded through a bearing plate, the ratio of experimental to predicated capacity was 1.11 with a coefficient of variance equal to 0.15.;The behavior of 24" deep FRP beams subjected to concentrated loads in the plane of the web was examined. Results showed that regardless of constitutive materials (polyester/glass or vinylester/glass) or loading (directly on flange or through bearing plate), deep specimens experienced local buckling of the web. Three theoretical equations were used to compare predicted and experimental quantities and yielded conservative results.;Eleven tests were conducted on 8" deep vinylester/glass pultruded beams with stiffening systems. Web bearing stiffeners, "doubler" plates, and stiffeners applied to the upper web-flange junction were found to increase capacity by 18% or more. "Doubler" plates and full-depth bearing stiffeners delayed formation of the "V"-shaped wedge in upper web-flange junction, but did not prevent it. Bearing stiffeners provided additional capacity and deflection after initial failure. Stiffening the upper web-flange junction increased capacity (62% average increase) and forced failure into the bottom web-flange junction.