This article investigates the behaviour of strengthened concrete columns using
jacketing ultra-high-performance fiber reinforced concrete (UHPFRC) and carbon
fiber-reinforced polymer (CFRP) under uniaxial loaded. The jacket was connected
to the column core using shear connectors and (CFRP) fixed as a strip on the
tension zone between the column cores and the jacketing. Seven column samples
of square cross-section (120 x120) mm at the midsection with overall length of
1250 mm were cast using normal strength concrete (NSC) and having similar
longitudinal and transverse reinforcement. The samples were made and tested
under axial load at eccentricity equal to 120 mm up to failure. Test parameters were
the thickness of jackets (25 and 35) mm and the width of CFRP (0,8, and 12) cm.
Column specimens were tested, one of them was reference without any
strengthening, and the other specimens divided into two groups (A, and B), and
each group included three specimens based on the parameters. Group (A) has
UHPFRC jacket thickness 25 mm and CFRP width (0,8, and 12) cm respectively,
and group (B) has UHPFRC jacket thickness 35 mm and CFRP width (0,8, and 12)
cm respectively. The outcomes of the article show that increasing the thickness of
jacket, and width of CFRP lead to increase in the load carrying capacity about
(110.5%,168.4%, and 184.2%) for group A, and (157.9%,226.3%, and 263.2%) for
group B compared with the reference column due to delay in the appearance of
cracks and their distribution. The mid-height lateral displacement of columns was
decreased about (66.6%,42.3%, and 35.9%) for group A, and (46.15%,38.46%, and
32.3%) for group B, also the axial deformation of specimens decreased about
(71.7%,60.86%, and 55.86%) for group A, and (65.5%,60.5%, and 53.4) for group
B compared with the reference column. The ductility of columns that were
strengthened with UHPFRC jacket only was increased about (13.67%,19.66%) for
thickness(25,35) mm respectively, because of that UHPFRC jacket was contented
on steel fibers, and the percentage decrease of ductility was about (5.1%,and 12%)
for group (A), (1%,and 9.4%) for group (B) when bonded CFRP in the tension zone
with width (8 ,and 12) cm respectively. The results show improvement in the initial
and secant stiffness when, increased the thickness of jacket, and width of CFRP
because of increase in the size of columns and improvement in the modulus of
elasticity. The toughness increase was about (273.97%,301.55%, and 304.5%) for
group A, and (453.69%,511.93%, and 524.28%) for group B compared with the
reference column because of increase in the size of specimens and delay the
appearance of cracks.
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