Civil Engineering Reference
In-Depth Information
b. Chisel off the cover of tested rebar, shown in Fig. 2.3, and attach strain gauges on the
exposed rebar, shown in Fig. 2.4.
Fig.2.3
Testing practical stress of rebar.
Fig.2.4
Layout of strain gauge.
c. Reduce the rebar section by grinding on the opposite side of the strain gauge. Then
measure the reduced amount of rebar diameter with square caliper and at the same time
record the increment of strain Δ
ε
s
through strain gauge.
d. The practical stress of rebar
σ
s
can be calculated according to the formula as follows.
n
Δ
ε
si
A
si
Δ
ε
s
E
s
A
s
A
s
i
=1
σ
s
=
+
E
s
f
y
(2
.
1)
n
A
si
i
=1
where Δ
ε
s
represents the strain increment of ground rebar.
Δ
ε
si
represents the strain
increment of the
i
th rebar near the tested rebar.
E
s
represents the elasticity modulus of
A
s
A
s
rebar.
refers to the section area of ground rebar, shown in Fig. 2.5(a).
represents
the area being ground off the rebar, shown in Fig. 2.5(b).
A
si
represents the section area
of the
i
th rebar near the tested rebar.
~
2
3
−
=
bh
A
s
D
b
~
A
s
−
A
s
(a)
(b)
Fig.2.5
Calculation for area of rebar after grinding
