Bridge Analysis, Design and Repair
341691 - A Hybrid Composite System for Strengthening Concrete Columns
Saturday, April 21
8:00 AM - 9:30 AM
Strengthening concrete beams and slabs using fiber-reinforced polymers (FRP) near-surface mounted (NSM) has gained a lot of research interest due to promising results. However, the method has not been effectively implemented for concrete columns due to possibility of buckling of NSM bars/strips. On the other hand, FRP-wrapping has been successfully used to enhance axial capacity of concrete columns with limited effect on bending performance. As majority of columns are subjected to combined axial load and bending moment, it is crucial for practicing engineers to enhance both axial and bending capacities. This paper proposes a hybrid system using both NSM and wrapping methods for concrete columns. The longitudinal NSM bars provide flexural strength and the transverse FRP wraps provide lateral support for the NSM bars and confinement for the concrete core. The FRP wrap also provides additional shear strength and protects the concrete core and existing steel bars against harsh environments. In this study, a total of 30 plain concrete cylinders (150 mm x 300 mm) were prepared, strengthened, and tested to isolate the effects of each method individually as well as to characterise the performance of the proposed hybrid system. Multiple glass FRP (GFRP) bars (#4) were mounted in 20 mm by 20 mm surface grooves, and unidirectional basalt FRP (BFRP) was used to wrap the specimens. Test parameters were number of NSM GFRP bars (4, 6, and 8) and number of BFRP layers (2, 4, and 6). The specimens were instrumented with multiple strain and displacement gauges and loaded under uniaxial compression. The hybrid system can provide a durable and cost-effective solution for rehabilitation of bridge and water front structures.