Glulam beams externally reinforced with CFRP plates

An experimental program was undertaken to investigate the effectiveness of carbon fiber reinforced polymer (CFRP) plates as flexural reinforcement of glued laminated timber (glulam) beams. Beams with and without reinforcement were tested up to failure in a four-point bending configuration. A comparison between the flexural behaviuor of control unreinforced beams with reinforced beams is shown and discussed. The results demonstrated increase in strength, stiffness and ductility when CFRP plate is bonded at tension side of cross section. Research findings indicated that the use of proposed reinforcing solution improves utilization of the compression characteristics of timber. Based on the experimental observations, a theoretical model is developed to predict the ultimate moment capacity and bending stiffness of CFRP-reinforced glulam beams.

Experimental investigation of cracked end-notched glulam beams repaired with GFRP bars

In this paper, an experimental research on bending behaviour of end-notched glulam beams and their bending behaviour after repairing with glass fibre reinforced polymer (GFRP) bars is presented. Altogether five glulam beams (100 x 220 x 4000 mm) made of spruce timber classified in the strength class C22 were tested. Experiment showed that originally, the beams failed in a brittle manner due to crack opening and its propagation. Cracks in the notch details were a result of excessive tensile stresses perpendicular to grain and shear stresses. Repairing the beams with GFRP bars after their failure completely restored and notably improved their load carrying capacity (average increase of 194%). Failure mechanism after repair changed from the original brittle tensile failure to more ductile failure in bending for most beams, proving the successfulness of the intervention. This study gives an insight in rehabilitation and repair possibilities of existing structures using advanced materials like GFRP bars.