Applied Loads and Stability of Steel and Steel-Concrete Composite Bridges - Finite Element Analysis and Design of Steel and Steel-Concrete Composite Bridges - page 135

(9.807 m/s 2 ), and R is radius of curvature of traffic lane in meters. Centrif-
ugal forces shall be applied horizontally at a distance of 1.8 m above the road-
way surface.
3.5 OTHER LOADS ON STEEL AND STEEL-CONCRETE
COMPOSITE BRIDGES
3.5.1 Fatigue Loads
Steel and steel-concrete composite bridges are subjected to a stress spectrum
and consequently fatigue owing to running traffic on the bridges. The stress
spectrum depends on the geometry of the trains or trucks, the axle loads, the
axle spacing, the composition of the traffic, and its dynamic effects. The cur-
rent codes of practice specify fatigue load models as guidance for the assess-
ment of fatigue load effects on highway and railway steel bridges.
3.5.1.1 Fatigue Loads on Highway Bridges
Specified in EC1 [ 3.1 ] are five fatigue load models of vertical forces on high-
way bridges. Fatigue Load Models 1, 2, and 3 are intended to be used to
determine the maximum and minimum stresses resulting from the possible
load arrangements on the bridge of any of these models. Fatigue Load
Models 4 and 5 are intended to be used to determine stress range spectra
resulting from the passage of motortrucks on the bridge. Fatigue Load
Models 1 and 2 are intended to be used to check whether the fatigue life
may be considered as unlimited when a constant stress amplitude fatigue
limit is given. Therefore, they are appropriate for steel constructions and
may be inappropriate for other materials. Fatigue Load Model 1 is generally
conservative and covers multilane effects automatically. Fatigue Load Model
2 is more accurate than Fatigue Load Model 1 when the simultaneous pres-
ence of several motortrucks on the bridge can be neglected for fatigue ver-
ifications. Fatigue Load Models 3, 4, and 5 are not numerically comparable
to Fatigue Load Models 1 and 2. Fatigue Load Model 3 may also be used for
the direct verification of designs by simplified methods. Fatigue Load Model
4 is more accurate than Fatigue Load Model 3 for a variety of bridges and of
the traffic when the simultaneous presence of several motortrucks on the
bridge can be neglected. Fatigue Load Model 5 is the most general model,
using actual traffic data. The load values given for Fatigue Load Models 1-3
are appropriate for typical heavy traffic on European main roads or
motorways.