Civil Engineering Reference
In-Depth Information
Figure 3.29
Cross-section and stress blocks for composite beam in
sagging bending
g
k
=
0.060
×
9.81
+
25
×
(0.406
×
0.178
−
0.0076)
=
2.20 kN/m
so the weight assumed earlier is correct.
For the effective flange width, it is assumed that two rows of stud
connectors are 0.1 m apart, so from Equation 3.55
b
eff
=
8.6/4
+
0.1
=
2.25 m
(3.110)
Assuming that for full shear connection, the depth
x
of the plastic
neutral axis is less than
h
c
(80 mm),
x
is found from Equation 3.56 with
f
cd
=
25/1.5
=
16.7 N/mm
2
:
N
c,f
= 7600 × 0.355 = 2.25
x
(0.85 × 16.7)
whence
x
=
84.6 mm
This exceeds
h
c
, so the correct
N
c,f
is given by Equation 3.58:
N
c,f
=
2.25
×
80(0.85
×
16.7)
=
2555 kN
From Equation 3.59,
N
a,pl
=
A
a
f
yd
=
7600
×
0.355
=
2698 kN
(3.111)
Assuming that the neutral axis is in the steel top flange, Equations 3.61 give
N
ac
=
2698
−
2555
=
143 kN
and
143
=
2
×
178(
x
c
−
150)
×
0.355
