ABSTRACT
Hybrid structural members, including concrete-filled FRP tubular sections, have great potential for beam and beam-column applications. Although the beneficial effects of confinement of concrete are significantly reduced in bending as compared to axially loaded members, other advantages such as utilization of the FRP shells as stay-in-place formwork, ease of fabrication, and speed of erection still make this system attractive. All the configurations shown in Figure 28.2 can be utilized in flexural members. In principle, the rule of the concrete is to resist the compressive stresses, while the FRP component is to resist the tensile stresses. However, in thin FRP-closed sections, the concrete has another important rule, mainly supporting the FRP shell in the compression side to avoid premature local buckling failure. In fact, this function of the concrete core gives the concrete-filled FRP tubular sections a major advantage over the hollow FRP ones, as indicated from a study by Fam and Rizkalla (2002). For example, the flexural strength of a filament wound FRP tube was increased by 212% by filling the tube with concrete. The same study has also shown that the higher the stiffness or the thickness-to-diameter ratio of the tube, the lower the gain in flexural strength and stiffness, resulting from concrete filling.
