Ehsan Ahmed

Flexural Performance of RC Beams Strengthened with Different Reinforcement Ratios of CFRP Laminates

In this paper, experimental study is carried out to evaluate the flexural performance of reinforced concrete beams strengthened with different ratios of carbon fibre reinforced polymer (CFRP) laminates. Four rectangular reinforced concrete beams strengthened with different reinforcement ratios of CFRP laminates are tested to failure under transverse bending on a simply supported span of 1.9 m. The increase of ultimate strength provided by the bonded carbon fiber is assessed and failure mode is identified. The results indicated that the flexural capacity of beam was significantly improved as the layers of laminates increased. It is concluded that the attachment of CFRP laminates has substantial influence on the performance of CFRP strengthened beams. However, de-bonding of CFRP laminates from the concrete surface is still a concern for the case of multi-layer strengthening of beam. Based on the observed results, recommendations are made to prevent the premature de-bonding failure of strengthened beams.

Immediate and Long-Term Deflection of Carbon Fiber Reinforced Polymer (CFRP) Concrete Beams

This study presents the results of immediate and long-term deflections of reinforced concrete beams strengthened with carbon fiber reinforced polymer (CFRP) laminates under sustained loading The test parameters were sustained load and different degrees of strengthening scheme for both cracked and un-cracked sections of beams. The applied sustained load was 56% and 38% of the ultimate static capacities of the un-strengthened beams for cracked and un-cracked section respectively. The long term deflections of CFRP strengthened beams at six month were on average 1.42 times the immediate deflections for un-cracked beams and 1.45 times the immediate deflections for cracked beams. The experimental results indicate that the long-term deflection of cracked beam shows significantly higher value compared to that of un-cracked beams. A comparison of time dependent deformation between analytical and experimental results shows closer agreement for the un-cracked beam sections. More conservative theoretical estimation is observed in the case of cracked beam section in spite the inclusion of tension stiffening effect. Finally, factors affecting the long-term deflection of strengthened beams are discussed to get better understanding on the long term behaviour of strengthened beams.

Deflection and cracking behavior of RC beams externally reinforced with carbon fiber laminates

This article presents the results and discussions of experimental and analytical work on CFRP-strengthened RC beams investigating the cracking and deflection performance. The aim of this study is to evaluate the time-dependent behavior by different degrees of strengthening scheme and two types of sustained loads. Eight RC beams were cast and tested under sustained loads for cracked and uncracked section. An analytical method based on EMM is developed to predict the time-dependent behavior of CFRP externally bonded RC beams. A simplified tension stiffening model for calculating the time-dependent deflection is modified for CFRP-reinforced concrete beams.