Durability studies on concrete columns encased in PVC¯FRP composite tubes

A new hybrid concrete column was developed for new construction. The proposed hybrid column, cast in place, consists of an exterior PVC¯fiber reinforced polymer (FRP) shell with a concrete core. The exterior shell is commercially available cylindrical PVC pipe externally reinforced with impregnated continuous fiber in the form of hoops at different spacing. The proposed system (PVC¯FRP) uses less fibers than current FRP confining methods but has similar strength and toughness characteristics. This paper present the results of an experimental study on the performance of hybrid concrete columns subjected to different environmental conditions such as room temperature, freeze and thaw, wet and dry conditions. Test variables included the type of fiber (carbon, aramid and glass), the spacing between the 200 and 400 freeze/thaw and wet/dry cycles. At the end of each exposure, the specimens were instrumented and tested under a uniaxial compressive test load. The stress¯strain behavior was used to evaluate the effect of exposure conditions on the strength, stress¯strain behavior and ductility of the confined specimens. Test results show that the external confinement of concrete columns by PVC¯FRP tubes results in enhancing compressive strength, ductility and energy absorption capacity. Durability tests show that the PVC¯CFRP confined specimens performed quite well under the severe exposures used in this study, whereas the PVC¯GFRP and PVC¯AFRP confined specimens experienced reductions in both strength and ductility.