In
this study, a lattice of steel grid tube, which is externally protected by a
FRP skin, is used to confine
square concrete
cylinders. Twenty seven
scaled-down square cylinders, which had a height of 308mm, a length of 114.3mm
and a width of 114.3mm, were prepared. In order to evaluate the effect of grids
on the structural performance of these encased square cylinders, two types of
grid tubes were used. Type 1 was prepared with ribs running in the axial
direction and Type 2 with ribs in a helical pattern. The specimens were divided
into 9
groups. Groups 1 and 5 had grids on one face; groups 2 and 6 had grids
on two opposite faces; groups 3 and 7 had grids on three faces and groups 4 and
8 had grids on all the four faces. Among them, Groups 1-4 were made of Type 1
grids and groups 5-8 were made of Type 2 grids. Solid steel tubes, Group 9,
which were also wrapped with the same FRP skin, were used to encase concrete
cylinders as controls. Uniaxial compression tests were conducted on all the
specimens. The effect of the steel grids on the structural behavior was evaluated
based on the test results.