Civil Engineering Reference
In-Depth Information
y
G
300
mm
z
400 mm
F
IGURE
12.3
Steel-reinforced timber beam
of Ex. 12.1
12
mm
100 mm
100 mm
b
b
b
t
E
t
E
s
d
b
F
IGURE
12.4
Reinforced
timber beam with steel
plates attached to its top
and bottom surfaces
t
E
s
E
t
b
(a)
(b)
(c)
and
300
3
12
=
10
6
mm
4
I
s
=
12
×
27
×
respectively. Therefore, from Eq. (12.7) we have
10
6
50
×
×
200
7
.
2N
/
mm
2
σ
t
=±
=±
×
10
6
+
×
×
10
6
1067
12
27
and from Eq. (12.8)
10
6
50
×
×
150
64
.
7N
/
mm
2
σ
s
=±
10
6
/
12
=±
10
6
27
×
+
1067
×
Consider now the steel-reinforced timber beam of Fig. 12.4(a) in which the steel
plates are attached to the top and bottom surfaces of the timber. The section may be
transformed into an equivalent timber beam (Fig. 12.4(b)) or steel beam (Fig. 12.4(c))
by the methods used for the beam of Fig. 12.1. The direct stress distributions are then
obtained from Eqs (12.7) and (12.8). There is, however, one important difference
between the beam of Fig. 12.1 and that of Fig. 12.4(a). In the latter case, when the
beam is subjected to shear loads, the connection between the timber and steel must
resist horizontal complementary shear stresses as shown in Fig. 12.5. Generally, it is
