Civil Engineering Reference
In-Depth Information
factors. The uniformly distributed loads should be applied only in the unfa-
vorable parts of the influence surface, longitudinally and transversally. LM1
is intended to cover flowing, congested, or traffic jam situations with a high
percentage of heavy motortrucks. Load Model 1 should be applied on each
notional lane and on the remaining areas. On notional Lane Number 1, the
remaining areas, the load magnitude is referred to as
a
qr
q
rk
. The values of
adjustment factors
a
Qi
,
a
qi
, and
a
qr
should be selected depending on the
expected traffic and possibly on different classes of routes. In the absence
of specification, these factors should be taken equal to unity. The character-
istic values of
Q
ik
and
q
ik
, dynamic amplification included, should be taken
the most unfavorable location. Where two tandem systems on adjacent
notional lanes are taken into account, they may be brought closer, with a
distance between wheel axles not below 0.50 m (see
Figure 3.7
)
.
Load Model 2 consists of a single axle load
b
Q
Q
ak
with
Q
ak
equal to
400 kN, dynamic amplification included, which should be applied at any
location on the carriageway. However, when relevant, only one wheel of
200
b
Q
(kN) may be taken into account. The value of
b
Q
should be specified.
The contact surface of each wheel should be taken into account as a rect-
angle with sides 0.35 and 0.60 m (see
Figure 3.8
)
. The contact areas of Load
Models 1 and 2 are different and correspond to different tire models,
arrangements, and pressure distributions. The contact areas of Load Model
2, corresponding to twin tires, are normally relevant for orthotropic decks.
For simplicity, the National Annex may adopt the same square contact
Key
X
1
Bridge longitudinal axis direction
1 Curb
2.00
X
0.60
0.35
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