Interaction diagrams for FRP strengthened RC rectangular columns with large aspect ratio

The load carrying capacity of reinforced concrete columns (RC) shall be enhanced by providing lateral confinement using fiber reinforced polymer (FRP). As per ACI 440.2R-08 [1], external strengthening using FRP composites is more effective for circular columns than rectangular columns having an aspect ratio greater than 2.0. The main objective is to develop column interaction diagrams for RC rectangular columns having an aspect ratio greater than 2.0 externally strengthened using FRP composites without any shape modification and subjected to combined axial load (Pn) and bending moment (Mn) due to lateral loading. Tests are conducted and semi-empirical equations developed for FRP strengthened RC rectangular columns with large aspect ratio. Pn-Mn interactions diagrams are developed using the semi-empirical solutions and validated with 3D finite element analysis. The column interaction diagrams are developed by varying the unconfined compressive strength of concrete, yield strength of steel, percentage of steel reinforcement and thickness of FRP composite. These diagrams shall be used for the design of FRP strengthened RC rectangular columns with large aspect ratio.