Abstract: Since columns are the most important elements of the
structures, failure of one column in a critical location can cause a
progressive collapse. In this respect, the repair and strengthening of
columns is a very important subject to reduce the building failure and
to keep the columns capacity. Twenty columns with different
parameters is tested and analysis. Eleven typical confined reinforced
concrete (RC) columns with different types of techniques are
assessment. And also, four confined concrete columns with plastic
tube (PVC) are tested with and with four paralleling tested of
unconfined plain concrete. The techniques of confined RC columns
are mortar strengthening, Steel rings strengthening, FRP
strengthening. Moreover, the technique of confined plain concrete
(PC) column is used PVC tubes. The columns are tested under
uniaxial compressive loads studied the effect of confinement on the
structural behavior of circular RC columns. Test results for each
column are presented in the form of crack patterns, stress-strain
curves. Test results show that confining of the RC columns using
different techniques of strengthening results significant improvement
of the general behavior of the columns and can used in construction.
And also, tested confined PC columns with PVC tubes results shown
that the confined PC with PVC tubes can be used in economical
building. The theoretical model for predicted column capacity is
founded with experimental factor depends on the confined techniques
used and the strain reduction.
Abstract: This paper investigates the viability of using carbon
fiber reinforced epoxy composites modified with carbon nanotubes to
strengthening reinforced concrete (RC) columns. Six RC columns
was designed and constructed according to ASCE standards. The
columns were wrapped using carbon fiber sheets impregnated with
either neat epoxy or CNTs modified epoxy. These columns were then
tested under concentric axial loading. Test results show that;
compared to the unwrapped specimens; wrapping concrete columns
with carbon fiber sheet embedded in CNTs modified epoxy resulted
in an increase in its axial load resistance, maximum displacement,
and toughness values by 24%, 109% and 232%, respectively. These
results reveal that adding CNTs into epoxy resin enhanced the
confinement effect, specifically, increased the axial load resistance,
maximum displacement, and toughness values by 11%, 6%, and
19%, respectively compared with columns strengthening with carbon
fiber sheet embedded in neat epoxy.