Civil Engineering Reference
In-Depth Information
Other design data from Chapter 3 are as follows:
structural steel:
f
y
=
355 N/mm
2
f
y
/
γ
A
=
355 N/mm
2
concrete:
f
ck
=
25 N/mm
2
f
ck
/
γ
C
=
16.7 N/mm
2
bar reinforcement:
f
sk
=
500 N/mm
2
f
sk
/
γ
S
=
435 N/mm
2
welded fabric:
f
sk
=
500 N/mm
2
f
sk
/
γ
S
=
435 N/mm
2
shear connectors:
60.2 kN
profiled steel sheeting: details as shown in Fig. 3.9; nominal thickness,
0.9 mm
composite slab: 150 mm thick, with T8 bars at 150 mm (top) above the
steel beams, and at 300 mm (bottom), shown in Fig. 3.12, and concrete
of Grade LC25/28
composite beam: steel section 406
P
Rk
=
75.2 kN
P
Rk
/
γ
V
=
178 UB 60, shown in Fig. 3.29, with
shear connection as in Fig. 3.30 and encased web as in Fig. 3.31, using
Grade C25/30 concrete. The properties of the concretes are given in
Table 1.4.
×
Many properties of the composite cross-section are required, so it is
useful to assemble them in a table, for ease of reference. The elastic and
plastic properties for major-axis bending, used in Chapter 3 or in this
chapter, are given in Table 4.5. The values of
A
and
I
for transformed
cross-sections are based on
E
210 kN/mm
2
. Values headed 'reinforced'
are for a cross-section with 679 mm
2
of top longitudinal reinforcement.
As explained later, the thickness of concrete slab above the sheeting is
taken as 95 mm for elastic properties and as 80 mm for plastic properties,
with the exception shown in Table 4.5. The depths
x
c
are from the top of
the concrete slab.
=
Table 4.5
Properties of cross-sections of a composite beam
Type of section
Cracked
Uncracked unreinforced
Cracked
unreinforced
reinforced
(I-section only)
Effective breadth, b
eff
, mm
—
2250
2250
1225
1225
1225
Modular ratio, n
—
10.1
20.2
10.1
20.2
—
Transformed cross-section,
7600
28 760
18 180
17 300
12 450
8279
A, mm
2
Depth x
c
of elastic neutral
353
129
176
177
231
327
axis, mm
(h
c
=
95)
(h
c
=
95)
(h
c
=
80)
(h
c
=
80)
Second moment of area,
215
751
636
—
508
278
10
−
6
I, mm
4
Depth x
c
of plastic neutral
353
151
151
—
—
300
axis, mm
(h
c
=
80)
(h
c
=
80)
M
pl,Rd
, kN m
424
829
829
—
—
510
sagging
sagging
hogging
