Enhancing Core Confinement in RC Columns Through Partial Tie Replacement with Welded Wire Mesh and CFRP Strips

Currently, reinforced concrete (RC) columns rely heavily on closely spaced steel ties for confinement and ductility under axial compression. However, tie congestion and construction limitations often reduce confinement efficiency, creating a need for alternative hybrid reinforcement solutions. A series of ten one-third scale circular RC short column specimens of 240 mm diameter and 1.2 m height were fabricated to investigate the effects of different internal confinement configurations. The columns were reinforced longitudinally with six steel rebars of 10 mm diameter (a steel ratio of 1%), and transversely with 6 mm diameter steel ties at varying spacings. All column specimens were cast using 25 MPa concrete, and their cores were internally wrapped with welded wire mesh (WWM) and carbon fiber reinforced polymer (CFRP) strips to enhance their confinement performance. The experimental program focused on evaluating the axial load capacity, axial strain, and ductility. Compared to control RC columns having conventional steel rebar ties, the specimens incorporating hybrid internal confinement of WWM and CFRP exhibited up to 38% and 180% increases in peak loads and ductility, respectively, and failed by buckling of the longitudinal steel bars, followed by rupture of the CFRP strips/WWM layers. These findings suggest that the use of internally wrapped composite systems in RC columns is particularly suitable for applications where dimensional constraints are critical. Additionally, an analytical model was proposed to predict the peak loads of the confined columns. The peak load predictions for various confinement configurations aligned well with the corresponding peak loads measured in experiments.