Experimental investigation on the flexural performance of glulam timber beams strengthened by near compression surface mounted (NCSM) CFRP plates

This paper presented an investigation on the performance of glued laminated timber (glulam) beams strengthened using CFRP plates mounted near the compression surface, or further named as near compression surface mounted CFRP (NCSM-CFRP). A total of eight specimens of glulam beams, 80 x 120 mm, comprising six strengthened beams and two unstrengthened control beams as reference, were tested to failure in a four-point bending scheme. The strengthened beams were varied in terms of depth, length, and number of CFRP plates. The test results confirmed that bending stiffness of the beam increased in the range of 19-56 %. However, modulus of rupture (MOR) and energy absorption capacity of the beams decreased compared to the average values of the control beams. In general, failure modes of the beams did not change from flexural tensile failure. The presence of CFRP plates only reduced, or even eliminated, the degree of plastification of the beams in compression zone. An analytical model was proposed, taking into account the contribution of CFRP plates, to predict elastic deflection and ultimate moment capacity of the beams. It was shown that the predicted results were in good agreement with the experimental results.