Mechanical Behavior of Concrete Columns Confined with CFRP Grid-Reinforced Engineered Cementitious Composites

Abstract

Using fiber-reinforced polymer (FRP) grid-reinforced engineered cementitious composites (ECC) for strengthening reinforced concrete columns and beams has been stirring structural research interest in recent years. The objective of this research was to extend the application of this technique, using carbon-fiber-reinforced polymer (CFRP). The authors used compression tests on short concrete columns strengthened with CFRP-ECC to investigate the mechanical behavior of strengthened columns by considering the unconfined concrete strength and reinforcement layers of CFRP grid. Test results show that the failure mode of most strengthened columns lies in the rupture of the embedded CFRP grid. The lateral strains corresponding to peak stresses were close, and their average value was almost equal to the ultimate axial tensile strain of the CFRP-ECC. Meanwhile, with an increased number of reinforcement layers, the peak stress and strain of the strengthening columns increased significantly for low-strength core concrete. However, there was no significant enhancement for the high-strength core concrete. In addition, the cracking stress of CFRP-ECC had obvious effects on the yielding stress, peak stress, peak strain, and the axial–lateral strain relationship. Most importantly, a better understanding of the stress–strain relationship for CFRP-ECC confined columns was established, and the feasibility of this model was verified by the analysis results.