Innovative Bridge Concept
9
sleepers and those elements are generally placed at a distance which can vary between
500 and 700 mm. The ballast layer not inferior 400 mm in depth is adopted in order
to guarantee the capacity of spreading and conveniently transmitting the loads that
are transmitted to the supporting structure without damaging the surface of a bridge.
However the influence of the mass of the bridge is quite significant. Increasing simply
the mass produces slightly unfavourably reduction of the critical resonant speed but
also beneficial decrease of the maximum vertical acceleration. But simultaneous
optimal increment on the mass and also the stiffness of the bridge may produce a
decrease of the maximum deflections and accelerations, without affecting the critical
speed.
For the aforementioned reasons, the steel bridge design is enabling them to gain
access into the higher speed lines, demonstrating their competitiveness and reliability.
In order to give an idea of the adaptation of the main structural characteristics of
ballasted steel bridges to the above requirements, a simple one span 30 m long plate
girders superstructure as another structural type used for crossing river is represented
in Fig. 7. Two side steel plate girders fabricated from web plate 14 mm thick had
to be reinforced by vertical stiffeners along the length and joined together with
lower flanges from flat steel 700 mm large and 50 mm thick. Floor beams 525 mm
high connected to girders from side to side and longitudinal stringers 250 mm high
running between these cross beams could create an orthotropic deck. This steel bed
holds ballasted deck with standard track on the ballast. Bottom and cross bracings
also contribute to stability. Figure 7 shows also the developed finite transformation
model.
Fig. 7 Ballasted single span 30 m long bridge and its finite numerical model
9
sleepers and those elements are generally placed at a distance which can vary between
500 and 700 mm. The ballast layer not inferior 400 mm in depth is adopted in order
to guarantee the capacity of spreading and conveniently transmitting the loads that
are transmitted to the supporting structure without damaging the surface of a bridge.
However the influence of the mass of the bridge is quite significant. Increasing simply
the mass produces slightly unfavourably reduction of the critical resonant speed but
also beneficial decrease of the maximum vertical acceleration. But simultaneous
optimal increment on the mass and also the stiffness of the bridge may produce a
decrease of the maximum deflections and accelerations, without affecting the critical
speed.
For the aforementioned reasons, the steel bridge design is enabling them to gain
access into the higher speed lines, demonstrating their competitiveness and reliability.
In order to give an idea of the adaptation of the main structural characteristics of
ballasted steel bridges to the above requirements, a simple one span 30 m long plate
girders superstructure as another structural type used for crossing river is represented
in Fig. 7. Two side steel plate girders fabricated from web plate 14 mm thick had
to be reinforced by vertical stiffeners along the length and joined together with
lower flanges from flat steel 700 mm large and 50 mm thick. Floor beams 525 mm
high connected to girders from side to side and longitudinal stringers 250 mm high
running between these cross beams could create an orthotropic deck. This steel bed
holds ballasted deck with standard track on the ballast. Bottom and cross bracings
also contribute to stability. Figure 7 shows also the developed finite transformation
model.
Fig. 7 Ballasted single span 30 m long bridge and its finite numerical model