The Design of Modern Steel Bridges - TEDI

156 The Design of Modern Steel Bridges
Hence the panel cannot be deemed restrained. Buckling coefficients for
rffiffiffiffiffiffiffi
b sy
¼ 120
t 355
and f ¼ 1:25
are obtained from Reference [2] as follows:
compression, K1 ¼ 0.270
bending, K b ¼ 0.975
shear, Kq ¼ 0.608
mc ¼
mb ¼
mq ¼
mc þ mb þ 3mq
176:8 1:1 1:05
0:27 355
103:2 1:1 1:05
0:975 355
60 1:1 1:05
0:608 355
1:00
¼ 2:13
2
¼þ0:119
2
¼þ0:103
Hence the panel is safe for buckling.
Web Stiffeners – Assume the two longitudinal stiffeners to be 100 10
plates and the transverse stiffeners to be 150 10 plates. The partial safety
factor g m for buckling of stiffeners in 1.20. With 32 times the thickness of the
web acting with the stiffeners, the following geometrical properties of the
stiffeners are relevant:
(i) Longitudinal stiffeners:
Centroidal moment of inertia, Isx ¼ 3165 10 3 mm 4
(ii) Transverse stiffeners:
Area of cross-section ¼ 4200 mm 2
Radius of gyration, r ¼ 27:45 mm
Centroidal moment of inertia, Isy ¼ 9375 10 3 mm 4
Area of cross-section ¼ 4700 mm 2
Radius of gyration, r ¼ 44:66 mm
(iii)
m ¼ Isx a
¼ 0:6077
b Isy
n ¼ a
¼ 0:6
B
Average spacing of longitudinal stiffener, b ¼ 833.3 mm.
To ensure that the orthotropic critical buckling load is not less than the Euler
buckling loads of the longitudinal stiffeners between transverse stiffeners, I sy