Strengthening of dapped timber beams using glass fibre reinforced polymer bars

Abstract

An economical rehabilitation scheme to strengthen creosote-treated dapped timber stringers in both flexure and shear is proposed. An experimental program was conducted to test stringers under monotonic load in three-point bending load configuration. Eight control beams with no reinforcement, 12 reinforced for flexure only, and 6 reinforced for flexure and shear were tested. Glass fibre reinforced polymer (GFRP) dowel bars were placed at an angle of 60° from the horizontal to reinforce for shear and to bridge the dapped end. Test results from previous studies by Gentile et al. (C. Gentile, D. Svecova, and S.H. Rizkalla. ASCE Journal of Composites for Construction, 6(1): 11–20, 2002.) and Svecova and Eden (D. Svecova and R.J. Eden. Canadian Journal of Civil Engineering, 31: 45–55, 2004) are combined with the results of this investigation for a total sample size of 54 beams. Large sample sizes are essential to study the performance of timber beams strengthened using GFRP bars in various schemes. An overall increase of 70% in the 10th percentile ultimate strength was obtained for stringers reinforced for both flexure and shear. Ductility was increased with the addition of the GFRP reinforcement, but the modulus of elasticity appeared to be unaffected.Key words: timber, bridge, glass fibre reinforced polymer, rehabilitation, modulus of rupture, analysis.