Design Examples of Steel and Steel-Concrete Composite Bridges - Finite Element Analysis and Design of Steel and Steel-Concrete Composite Bridges - page 382

This process is commonly called as curtailment (transition) of flange plates.
It should be noted that, theoretically, curtailment (transition) of flange plates
can be conducted by reducing the flange plate width, thickness, or both.
However, in practice, fabricators prefer to keep the flange widths constant
and vary the thickness because this option costs much less than reducing the
flange width, which might require a very heavy grinding work. To avoid
lateral torsional buckling of the compression top flange at the reduction
zone, it is recommended practically to reduce the width or thickness by
40% of the original with a smooth transition zone sloping at 1 (vertical)
to 10 (horizontal). It is also recommended that bridges with lengths of
20-30 m are curtailed in one step, while for bridges with spans greater than
30 m, two steps of curtailment (transition) are recommended. For the inves-
tigated design example, we can conduct one-step curtailment by reducing
the top flange plate of the upper and lower flanges, as shown in Figure 4.144 .
To classify the reduced cross section,

s

235
f y

r

235
275

e ¼ ¼ ¼ 0 : 924

3

36.7

55

145.3

57

y y

270 cm

y 1 y 1

1.6

130.7

135

y 0

y 0

54

Figure 4.144 Calculation of properties of area for curtailed main plate girder.