Stability and failure characterization of fiber reinforced pultruded beams with different stiffening elements, Part I: Experimental investigation

Abstract

The un-stiffened fiber reinforced polymer (FRP) beams under three-point bending often fail at compression web-flange junction due to low inter-laminar shear and transverse compressive strengths of web. Therefore, the objective of the present work is to study the effect of different stiffening elements on the flexural response of FRP I-beams. Various stiffening elements such as glass fiber reinforced polymer (GFRP) cover plates, cover angles, and bearing stiffeners are connected to the beam separately to examine their effect on the strength, stiffness and failure modes. This study also includes the strengthening of web-flange junction of FRP I-beams using carbon fiber layers with adhesive. It is observed that replacing the chopped strand mats with 45° and 90° unidirectional rovings increases the crushing strength of the beam. Strengthening of web-flange junction using carbon fiber layers or stiffening with short length bearing stiffeners under loading is observed to be most effective in preventing the failure of web-flange junction of FRP I-beams. Beams stiffened with short length bearing stiffeners have higher failure load than other stiffened beams. Strengthening of web-flange junction using wet carbon fiber layers is noted to be more effective than stiffening with GFRP cover angles. Since the stress concentration produced due to the sudden change in the cross-section of beams strengthened with carbon fiber reinforced polymer (CFRP) laminated cover angle is less than that for beams stiffened with GFRP cover angles.