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IBRACON Structures and Materials Journal • 2013 • vol. 6 • nº 2
Influence of steel fibers on the reinforcement bond of straight steel bars
16% the bonding stress between bar and concrete. In this case,
the results were obtained by pull-out tests conform to literature [3],
on bars of 8 mm and 20 mm of diameter embedded in concrete
with compressive strength of up to 93 MPa. Despite this result, in
general these researchers noted a reduction of up to 45% in nor-
malized bonding stress due to the addition of steel fibers.
In Figure 5, the average bonding stress between bar and concrete
Figure 3 – Pull-out test setup (dimensions in mm)
Table 3 – Results of concrete properties and pull-out test
Test
specimen
F
max
(kN)
f
b
(kN)
Bonding
length
f
cm
(MPa)
f
ctm,sp
(MPa)
E
cm
(GPa)
G
f
2
(N.m/m )
(1)
CP10.5.0.A1
(1)
CP10.5.0.A2
(1)
CP10.5.1.A1
(1)
CP10.5.1.A2
(1)
CP10.5.2.A1
(1)
CP10.5.2.A2
(2)
CP10.10.0.A1
(2)
CP10.10.0.A2
(1)
CP10.10.0.A3
(2)
CP10.10.0.A4
(2)
CP10.10.1.A1
(2)
CP10.10.1.A2
(2)
CP10.10.1.A3
(2)
CP10.10.1.A4
(1)
CP10.10.2.A1
(1)
CP10.10.2.A2
(3)
CP10.10.2.A3
(3)
CP10.10.2.A4
31.9
32.6
31.2
38.8
32.0
31.4
46.9
50.5
39.1
46.1
52.8
51.4
48.7
48.7
34.0
31.3
45.9
51.4
20.31
20.75
19.86
24.70
20.37
19.99
14.93
16.07
12.45
14.67
16.81
16.36
15.50
15.50
10.82
9.96
–
–
5
10
58.70±3.86
73.20±2.72
± 67.80 0.98
± 58.70 3.86
58.90±3.32
± 73.20 2.72
66.98±7.16
67.80±0.98
± 69.96 1.39
5.98±0.05
8.12±1.08
10.80±0.46
5.98±0.05
4.84±0.44
8.12±1.08
8.74±0.49
10.80±0.46
9.17±0.39
28.33±0.35
30.97±0.21
± 30.00 0.60
± 28.33 0.35
± 29.03 0.48
± 30.97 0.21
± 31.90 0.80
30.00±0.60
34.67±0.40
0.062±0.019
–
–
± 28.33 0.019
ND
–
–
–
–
ND: non-determined value. (1) The pull-out of the bar happened before the yield of the steel; (2) the pull-out of the bar
happened after the yield stress of the steel, but before its failure; (3) the failure happened in the bar, without it being pulled out.
Figure 4 – Test specimen preparation detail
1...,131,132,133,134,135,136,137,138,139,140 142,143,144,145,146,147,148,149,150,151,...190