Combined effects of freeze-thaw and sustained loads on reinforced concrete beams strengthened with FRPs
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Fibre reinforced polymer (FRP) materials have emerged as an innovative tool within the civil engineering community for the strengthening and rehabilitation of existing reinforced concrete structures. Research has taken place over the past decade that has demonstrated the benefits of FRPs, and it is evident that there is a need for their usage given the status of the deteriorated North American civil infrastructure. However, in order to increase confidence in the application of these materials in Canada, further information is required to fully understand their behaviour in cold climates. This thesis expands on the previous research that has taken place at Queen’s University, investigating the freeze-thaw behaviour of FRP strengthened reinforced concrete. The research program herein studies the combined effects of freeze-thaw cycling and sustained loading on the flexural performance of 45 small-scale beams strengthened with glass FRP sheets, carbon FRP sheets, or carbon FRP plates. In an attempt to attain failure of the beams due to FRP rupture, the anchorage of the beams was increased and a theoretical model was produced to select the beam design for this failure mode. The model also predicted the performance of the strengthened beams in order to determine appropriate sustained loading levels. After being subjected to 300 freeze-thaw cycles and almost 3 months of sustained loads, the beams were tested to failure. It was found that the beams subjected to combined loads encountered virtually no losses in average ultimate strength. However, the greater inconsistency of the results for these beams relative to the control beams implies that lower guaranteed strengths should be used for design in situations where these conditions are present.