Fig. 2: Rendering of the bridge
1.4. Other Elements
The deck is supported by spherical bearings except at
the fixed point, where the arch is monolithically linked
to the deck.
Box abutments with intermediate walls are designed
with maximum heights of 8.63 m at one end and 9.64
m at the other. The bearings and expansion joint
devices are supported by these.
Environmental issues with birds made it necessary to
use railway edge barriers 3.00 m high. The barrier is
formed by steel curve tubes 100 mm diameter every
0.50 m. In the lower part longitudinal horizontal tubes
with differing diameters are used. The aerodynamic
behavior of this barrier was tested with satisfactory
results.
2. CONSTRUCTION PROCESS
2.1. General definition of the deck construction
The deck is built by a movable scaffolding system,
consisting of a steel truss. The steel truss is supported
by two adjacent piers, this being the chosen for
method every span of the viaduct.
To avoid excessive stresses in the arch, the erection of
the spans over it was symmetrical. The deformation of
the arch and an interaction between the elements of
the bridge was considered in the design.
2.2. General definition of the arch construction
The arch is erected from both sides of the bridge
concurrently, and was supported by diagonal cable
stays strung from the adjacent piers and two steel
temporary towers. The towers were in turn stayed to
the foundations of the next two piers as they needed
to be anchored to the ground to withstand the loads
exerted by the stays.
For each semi-arch, several auxiliary elements are
needed: A steel tower was placed over the piers and;
a form traveler system. A group of cable-stays was
4/2016
used to support the built part of the semi-arch, it was
anchored to the tower and piers to maintain the
equilibrium of the tower. The pier was anchored to
the foundations and the foundations in turn anchored
to the ground.
Each steel temporary tower was composed by two
columns at a distance of 6.50 m joined by a K bracing.
The section of each column is a hollow steel box.
The tower width is reduced where the tower meets
the deck, to allow a correct transmission of the loads
to the pier top.
The bracing system is composed of horizontal beams
placed at 4.00 m spacing and diagonal elements that
form a K turned 90 degrees. The bracings were steel
double T fabricated cross sections.
The form traveler system was also a steel structure
designed to support the formwork of each arch
segment which allows the concrete to be cast in
place. It was a cantilever structure, with a weight of
95 tonne attached to the already executed and
hardened part of the arch.
The arch is composed of 93 segments each about 3.80
m long.
Regarding the cable-stayed system, 15 pairs of stays
supported each semi-a rch and another 15 pairs held
each tower. A pair of stays was placed in the arch
every three segments.
Tower cranes:
Materials (reinforcing bars, concrete and prestress)
were taken to the form traveler system through two
tower cranes installed on each semi-arch.
As in other major infrastructure projects, auxiliary
structures are key to the satisfactory completion of
the works. The project had a system of four tower
cranes and temporary stairs to access the 70 m high