Civil Engineering Reference
In-Depth Information
To assume a reasonable cross section for the upper chord compression
member, the following parameters can be considered:
a
12
15
¼
5000
12
15
¼
417
333mm,
h
w
¼
taken as 400 mm
:
b ¼
0
ð
:
75
0
:
Þh
w
¼
0
ð
:
75
0
:
Þ
400
9
9
¼
300
360mm,
taken as 360 mm
:
It should be noted that the spacing between gusset plates (
b
) must be kept
constant for the whole truss. Let us start by assuming the upper cover plate
width of 500 mm, flange thickness of 36 mm, and web thickness of 24 mm.
After that, we design the member and check the stresses. If the section is safe
and economic, then the design is acceptable; otherwise, we change the
dimensions accordingly and repeat the procedures. To classify the cross sec-
tion chosen (see
Figure 4.192
)
,
s
235
f
y
r
235
275
e ¼
¼
¼
0
:
924
b ¼
360mm,
t
fl
¼
36,
b
=
t
fl
¼
360
=
36
¼
10
<
30
:
5 Flange is Class 1
ð
Þ
C ¼
340mm,
t
w
¼
24,
C
=
t
fl
¼
340
=
24
¼
14
:
<
:
ð
Þ
2
30
5 Web is Class 1
6cm
2
A¼
50
3
:
6+36
3
:
6+2
40
2
:
4
¼
501
:
50
3
:
6
21
:
8
36
3
:
6
16
:
8
e ¼
¼
3
:
74 cm
501
:
6
I
m
¼
2
2
:
4
40
3
=
12 + 50
3
½
:
6
3
=
12 + 50
3
:
6
21
:
8
2
6
3
8
2
¼
143831 cm
4
+36
3
½
:
=
12 + 36
3
:
6
15
:
74
2
¼
136815 cm
4
I
x
¼
143831
501
3
:
6
50
3
6
36
3
4
3
2
2
I
y
¼
3
:
=
12 + 3
:
=
12 + 2
40
2
:
=
12 + 40
2
:
4
19
:
¼
122368 cm
4
r
I
x
A
r
136815
501
i
x
¼
¼
¼
16
:
52 cm
:
6
r
I
y
A
r
122368
501
i
y
¼
¼
¼
15
:
62 cm
:
6
l
b
x
¼ l
b
y
¼
5000mm
L
cr
i
1
l
1
l¼
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