Novel filament wound FRP grid tubes for reinforcing concrete structures : concept and behaviour

Abstract

Filament wound FRP grid tubes (FGTs) are a novel form of FRP reinforcement recently developed at The Hong Kong Polytechnic University. FGTs are produced through an automated filament winding process which effectively eliminates the fibre kinking issues and the overlapping regions in pultruded FRP bent bars and minimises the on-site work for forming reinforcement cages. FGTs can be made into various convex shapes (e.g., circular, oval, triangular, quadrilateral, and octagonal shapes) to suit different needs for reinforcement. They may serve as a confining device in columns or piles, as shear reinforcement in beams, and as major tensile reinforcement in walls or two-way slabs. For large structural members such as wave walls and dams, FGTs may also serve as a crack control measure against thermal effects from concrete hydration and/or temperature variations. This paper presents the concept of FGTs as well as two experimental studies demonstrating their expected advantages. One of the studies involved the testing of a series of FGT-reinforced concrete columns and demonstrated that the FGTs can provide effective confinement to the concrete, leading to a ductile response of the columns. The other study involved three-point bending tests of FGT-reinforced concrete beams and showed that the FGTs can effectively enhance the shear capacity of concrete beams.