1. INTRODUCTION AND CONTEXT
The characteristics of HSR traffic requires the
alignment to comply with strict design parameters
both in horizontal and vertical profile and leads to
numerous bridges, commonly with significant length
and sometimes also height. These bridges and
viaducts, which are inevitably flexible elements of rail
schemes, are subjected to heavier vertical and
horizontal loads than road bridges. They have also to
comply with strict deflection and vibration limits in
order to guarantee passenger comfort and traffic
security (assuring that railroad geometry and
curvature, together with wheel-rail contact, are
maintained). Additionally, HSR bridges are exposed to
considerable dynamic effects, are prone to suffer from
fatigue problems due to the intensity and
repetitiveness of the loads, and have global-length
limitations due to rail expansion joints capacities and
track-structure interaction.
Almonte River close to its mouth, where it flows into
the Alcántara Reservoir.
As a consequence of these characteristics, HSR bridge
spans tend to be shorter than bridges carrying other
types of traffic. Nevertheless, there are sometimes T
obstacles which inevitably require span lengths above
the customary and can be considered exceptional for
the combination of rail traffic, as in the case of the
Almonte bridge described in this article.
All these particularities make the design and
construction of this major bridge a challenge.
The new HSR line at the Madrid- Portuguese Border
(with mixed-use and a maximum speed of 330 km/h
for passengers and 100 km/h for freight) crosses the
The importance of the location from the
environmental point of view makes it impossible to
arrange supporting elements inside the reservoir
infringing on the maximum water level limits, leading
to a 350-m distance to be cleared between banks. This
made necessary a bridge with a main span of 384 m,
the largest on the Spanish HSR network and the third
longest concrete arch in the world.
The magnitude of such a main span implies additional
requirements to those inherent to any HSR previously
built. As an example, aeroelastic phenomena
(increasing oscillations caused by the interaction
between wind and structure) can be significant for
these spans and must be considered in the design.
The total length of the entire viaduct is 996 m.
The conceptual and detailed design of the viaduct was
carried out by Arenas & Asociados, within a Joint
Venture with IDOM for the design of a complete
infrastructure subsection (Alcántara ReservoirGarrovillas) of the Madrid- Portuguese Border HSR
line. Adif (the Spanish Administrator of Railway
Infrastructure) is the owner of the infrastructure and
the client. FCC in Joint Venture with Conduril is
responsible for the construction of the bridge.
Fig. 2: Site image and bridge alignment
4/2016