Behavior of FRP Composite Wrapped Concrete Cylinders with Embedded Debonds

Abstract

A major application of composite materials in the reinforced concrete industry is to wrap concrete columns with Fiber Reinforced Polymer (FRP) composite fabric which results in increase in the columns’ axial compressive strength and ductility. Presence of debonds between the FRP wrap and the underlying column surface inhibits the proper confinement of the column by the composite wrap. This research studies the effect of debonds on stress-strain behavior of FRP wrapped concrete cylindrical specimens. All laboratory tests were conducted on concrete cylinders of size 6’’ x 12’’ (152.4 mm x 304.8 mm). Simulated air-filled debonds, water-filled debonds and debonds made from Teflon sheets of various sizes were placed on the concrete cylinder’s surface prior to wrapping with carbon or glass FRP fabrics. The FRP wrapped cylinders were tested to failure in compression, and the effect of debond area in terms of percentage of total area on the stresses and strains of the concrete cylinders was established. The results showed a significant decrease in axial compressive strength with an increase in area of debonds, and appropriate reduction factors have been proposed for use in strength computations. Both GFRP and CFRP composites were found to be effective in arresting the lateral dilation of the underlying concrete. Also, considerable ductility enhancement was evident in the FRP wrapped cylinders, particularly with CFRP composites.