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IBRACON Structures and Materials Journal • 2013 • vol. 6 • nº 1
L. A. SPAGNOLO JR | E. S. SÁNCHEZ FILHO |
M. S. L. VELASCO
The effective stress has a non-uniform distribution, and at ultimate
state is defined as:
(13)
max ,
,
f
f
ef f
D f
and the maximum stress is given by
(14)
with
(15)
sin
1
sin
2
f
f
f
f
w
s
w
s
w
(16)
c
f f
e
f
tE
L
(17)
e
L
L
max
(18)
2
sin
L
(19)
2
sin
2
cos 1 2
f
D
4. Experimental investigation
4.1 Test specimens
Eight
T
reinforced concrete beams 3.00
m
long were tested ([14]).
All the specimens were designed to have the same nominal cross
sectional dimensions:
b
w
= 15
cm
and
h
= 40
cm
. Cross‑sectional
details of the beams are shown in Figure [3]. The specimens were
also designed to be tested with a constant ratio
a/d
= 87.5/36 = 2.4.
The testing program was divided into two series with four beams
tested as part of each series. In each series, one beam had no CFC
reinforcement (reference beam), but the internal steel reinforcement
was the same as that of the beams in the series. Specimens were la-
beled by the explanatory label: 1) Series I was one reference beam
VR1 and three strengthened beams with
U
stirrups, with either one,
two or three layers of CFC, VI‑1, VI‑2, VI‑3, respectively; and 2) Se-
ries II was one reference beam VR2 and three strengthened beams
with
U
stirrups, with either one, two or three layers of CFC, VII‑1,
VII‑2 e VII‑3, respectively. Series II had fewer internal steel stirrups
in the midspan of the beam (bending zone) than Series I.
All CFC
U
stirrups 10
cm
x 79
cm
were glued on to concrete sur-
face, and a 5
cm
x 87.5
cm
longitudinal strip (one layer of CFC)
was fixed to the ends of the stirrup on both sides of the beams, as
shown in Figures [4] and [5].
The beams in each series were cast simultaneously from the same
batch of concrete, and consolidated with internal vibrators.
Table [1] presents a summary of the properties of the steel rein-
forcement (transverse reinforcement ratio), including the thickness,
width and transverse ratio of the CFC reinforcement (variables of
this research). Details of the beams are presented in Figure [6]. To
prevent premature localized failure (anchorage failure), both ends of
the beams were heavily reinforced and longitudinal bars were care-
fully anchored.
Figure 3 – Geometry of test beams