A new approach for the strength interaction diagram of FRP strengthened square steel reinforced high strength concrete columns

Abstract

This paper proposed a new approach for the strength interaction diagram (N‐M diagram) of FRP strengthened square steel reinforced high strength concrete (SSRHSC) column, considering the influence of the applied load eccentricity on the ultimate conditions of FRP strengthened high‐strength concrete (HSC). The analytical model for the strength interaction diagram of FRP strengthened SSRHSC (FRPS‐SSRHSC) columns, which incorporated the stress–strain models of constitutive materials into the rectangular stress block (RSB) method, was developed and verified against test data. The strength interaction diagrams of FRPS‐SSRHSC columns developed based on the proposed analytical model matched well with the test results, while the strength interaction diagrams developed using available design codes overestimated the experimental strength interaction diagrams. The effect of confinement ratio and longitudinal FRP strengthening on the strength interaction diagrams was examined via parametric analyses. It was found that longitudinal strengthening had a negligible influence on the axial load and bending moment when the axial load was applied at a small eccentricity but had a substantial influence when the axial load was applied at a large eccentricity.