In
this study, an advanced grid stiffened (AGS) composite tube, which was made of
a lattice of interlaced fiber
reinforced polymer (FRP) ribs that was wrapped by
a FRP skin, was used to encase
concrete cylinders. Two types of cylinders were
prepared. One was a
circular cylinder and the other was a square cylinder. For
the circular cylinders, a uniaxial compression test was conducted; for the
square cylinders, both uniaxial compression test and four-point bending test
were conducted. The test results showed that the AGS tube confined concrete
cylinders displayed a considerable positive composite action due to the
mechanical interlocking. The AGS tube provided an “active” confinement to the
concrete core. The elastic range and the specific axial strength of the
circular AGS cylinders, and the specific bending strength of the square AGS
beams were higher than those encased by solid FRP tubes, solid steel tubes, or
steel grid tubes. The square AGS tubes were not as effective as the circular
AGS tubes in confining concrete.