Numerical Investigation of the Influence of FRP Strip Confinement Parameters on the Monotonic Flexural Behaviour of RC Columns

To further investigate the influence of FRP strip confinement parameters on the flexural behaviour of RC columns under monotonic lateral loading, a three-dimensional solid finite element model was established in ABAQUS, and numerical simulations together with parametric analyses were carried out for RC columns under unconfined, fully confined, and partially confined conditions. The results show that full-length FRP confinement increased the peak load of the column to about 390 kN, over 60% higher than that of the unconfined column, while reducing post-peak softening and damage at the column base. For strip spacings of 100, 150, and 200 mm, the peak loads of the partially confined columns were all higher than that of the unconfined column; in particular, the 100 mm spacing model reached about 315 kN, with an increase of approximately 31%. When FRP strips were locally arranged at the column ends, the peak load was about 305 kN, and the overall response was close to that of the 100 mm spacing model with reduced FRP usage. At a lateral displacement of 35 mm, the maximum equivalent stresses in the FRP strips of CJ100 and CH1 were about 2654 MPa and 1936 MPa, corresponding to 61.0% and 44.5% of the tensile strength, respectively, indicating that the confinement effect of the FRP strips was not fully mobilized. Appropriately reducing the strip spacing and prioritising reinforcement in critical regions such as the column base can improve the monotonic flexural performance of RC columns while enhancing the utilisation efficiency of FRP materials. The results may provide a reference for the configuration optimisation of FRP strip strengthening for RC columns under monotonic lateral loading.