Civil Engineering Reference
In-Depth Information
z
e
20 m
z
e
¼50 m
0.5
5.7
7.1
4.0
3.1
3.8
such as grass and isolated obstacles with separations of at least 20 obstacle
heights. The value of the directional factor,
c
dir
, for various wind directions
may be found in the National Annex wherein the recommended value is 1.0,
whereas the value of the season factor,
c
season
, may be given in the National
Annex with a recommended value of 1.0. The wind load factor
C
can be
calculated as follows based on
c
e
, which is the exposure factor given in
C ¼ c
e
c
f
,
x
ð
3
:
3.4.3 Horizontal Forces on Highway Steel and Steel-Concrete
Composite Bridges
3.4.3.1 Braking and Acceleration Forces
Similar to railway bridges, highway steel and steel-concrete composite brid-
braking force,
Q
lk
, shall be taken as a longitudinal force acting at the surfac-
ing level of the carriageway. The characteristic value of
Q
lk
limited to
900 kN for the total width of the bridge and should be calculated as a fraction
of the total maximum vertical loads corresponding to the Load Model 1
likely to be applied on Lane Number 1, as follows:
Q
1k
¼
0
1
a
q1
q
1k
w
1
L
180
a
Q1
k
ðÞQ
1k
900 k
ðÞ
:
6
a
Q1
2
Q
1k
ð
Þ
+0
:
ð
3
:
16
Þ
where
L
is the length of the deck or part of it under consideration. For exam-
ple,
Q
lk
¼
360+2.7
L
(
900 kN) for a 3 m wide lane and for a loaded length
L
1.2 m, if
a
factors are equal to unity. The upper limit (900 kN) may be
adjusted in the National Annex. The value 900 kN is normally intended to
cover the maximum braking force expected to pass over the bridge. Hori-
zontal forces associated with Load Model 3 should be defined where appro-
priate. This force should be taken into account as located along the axis of
any lane. However, if the eccentricity effects are not significant, the force
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