Timber Beams Strengthened with GFRP Bars: Development and Applications

Repair and rehabilitation of infrastructure is becoming increasingly important for bridges due to material deterioration and limited capacity to accommodate current load levels. An experimental program was undertaken to study the flexural behavior of creosote-treated sawn Douglas fir timber beams strengthened with glass fiber-reinforced polymer (GFRP) bars. Twenty-two half-scale and four full-scale timber beams strengthened with GFRP were tested to failure. The percent reinforcement ratios were between 0.27 and 0.82%. Additional unreinforced timber beams were tested as control specimens. The results have shown that using the proposed experimental technique changed the failure mode from brittle tension to compression failure, and flexural strength increased by 18 to 46%. Research findings indicate the use of near-surface GFRP bars overcomes the effect of local defects in the timber and enhances the bending strength of the members. Based on the experimental results, an analytical model is proposed to predict the flexural capacity of both unreinforced and GFRP-reinforced timber beams. The article also reviews implementation of the proposed technique for strengthening a timber bridge near Winnipeg, Manitoba, Canada.