Ductility of timber beams strengthened using carbon fiber reinforced polymer plates

Abstract

This research was conducted to investigate the behavior of timber beams strengthened with carbon fiber reinforced polymer (CFRP) plates using Sikadur - 30 as bonding agent. The surface to be bonded was spiked by punching small holes of 2 mm in diameter with 10 mm spacing. The aim is to increase bonding capacity by having small studs when Sikadur - 30 is applied to the timber surface. Although from the previous research shows that the strength was increased, the ductility of the strengthened bea ms needs to be studied as the ductility contributes to the failure modes. Five beams with the dimension of 100 mm 200 mm 3000 mm were tested where one of the beams was used as control beam (unstrengthened). The remaining beams were strengthened with di fferent configurations before tested to failure under four - point loading. The ductility behavior of the beams was studied based on their load - deflection characteristics. The results showed that the strengthened beams performed better than the control beam where the ductility were increased as the percentage of CFRP was increased. The ductility was dramatically improved where the highest ductility index based on deflection method was 2.2 where the percentage increase was 37.5% whereas the highest ductility index based on energy method was 3.2 where the percentage increase was 88.2% . From this studies, it was found that 0. 3 % is the optimum value of CFRP area to achieve maximum ductility index. Ductility index obtained from energy method gives higher values when compared to deflection method for all values of CFRP area. All beams in this study did not fail due to peel off or debonding. It also proved that the spikes that have been made at the wood surface were very effective for bonding. These spikes were new technique introduced in this strengthening scheme .