Title: Axial Compression-Flexure Interaction Behavior of Hybrid Fiber-Reinforced Polymer-Strengthened Columns
Author(s): M. Chellapandian and S. Suriya Prakash
Publication: Structural Journal
Appears on pages(s): 125-138
Keywords: axial compression; flexure; hybrid strengthening; interaction diagram; near-surface mounting (NSM) strengthening; reinforced concrete (RC) columns
Fiber-reinforced polymer (FRP) composites are widely used for strengthening of reinforced concrete (RC) elements under different loading conditions. This paper aims at understanding the axial compression-bending moment (P-M) interaction behavior of RC columns strengthened with different carbon FRP (CFRP) techniques—namely, 1) near-surface mounting (NSM); 2) external bonding (EB); and 3) hybrid NSM and EB CFRP strengthening. P-M interaction behavior was analyzed under different loading combinations: 1) axial compression with zero eccentricity (e = 0); 2) uniaxial eccentric compression (e/d = 0.15 and 0.63); and 3) pure bending (e = ∞). Analytical predictions of axial compression-bending moment interaction were compared with the experimental results. Interaction diagrams were developed using the strain compatibility procedure for two scenarios: 1) ignoring the contribution of NSM laminates under compression; and 2) including the contribution of NSM laminates under compression. The analytical predictions exhibited a good correlation with the test results when the contribution of NSM laminates under compression was included. Hybrid strengthening was found to be efficient in improving the strength without much reduction in ductility under all loading combinations. An extensive parametric investigation was carried out for understanding the effect of various parameters such as concrete compressive strength, EB, and NSM CFRP reinforcement ratio, and conclusions were derived.