Design Examples of Steel and Steel-Concrete Composite Bridges - Finite Element Analysis and Design of Steel and Steel-Concrete Composite Bridges - page 290

55 cm

3.6

C = 39

e = 4.36

x x

h w = 45

m m

2.4

2.4

3.6

2 .4

Gusset plate

b = 40

Figure 4.67 The cross section of the maximum compression member U 5 as well as that
of the member U 4 .

for the upper chord compression member, the following parameters can be
considered:

a
12 15 ¼

6000
12 15 ¼ 500 400mm, taken as 450mm

h w ¼ :

b ¼ 0 ð : 75 0 : 9 Þ , h w ¼ 0 ð : 75 0 : 9 Þ 450

¼ 337 : 5 405mm, taken as 400mm :

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 550 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
section chosen (see Figure 4.67 ),

s

235
f y

r

235
275

e ¼ ¼ ¼ 0 : 924

b ¼ 400mm, t fl ¼ 36, b = t fl ¼ 400 = 36 ¼ 11 : 1 < 30 : 5 Flange is Class 1 ð Þ

C ¼ 390mm, t w ¼ 24, C = t fl ¼ 390 = 24 ¼ 16 : 25 < 30 : 5 Web is class 1 ð Þ

4 ¼ 558 cm 2 A¼ 55 3 : 6+40 3 : 6+2 45 2 :

55 3 : 6 24 : 3 40 3 : 6 16 : 5

e ¼ ¼ 4 : 36 cm

558