Semi-empirical solutions are proposed to predict the axial and lateral capacities of reinforced concrete (RC) rectangular columns having aspect ratio greater than 2.0 strengthened using fiber reinforced polymer (FRP) composites without any shape modification and subjected to axial, lateral and combined axial and lateral loading. 3D finite element models are generated for the analysis of FRP strengthened RC columns. Semi-empirical solutions and finite element models are validated with the test results. Column interaction diagram between axial capacity Pn and bending moment Mn is generated using the proposed semi-empirical solutions and compared with Pn - Mn interaction diagram generated as per ACI 440.2R-08 [1] procedure. From this study, it is concluded that the proposed semi-empirical solutions shall be used for the design of RC rectangular columns having aspect ratio greater than 2.0 strengthened with FRP composites and without any shape modification. © 2018