2.3. Optimization of the construction process of the
arch
During the development of the works, a number of
modifications were studied to optimize the use of
resources, time and materials.
The main change made to optimize the construction
process was in the anchoring of cable stays to the
concrete pier next to the arch. This would result in the
possibility of starting the construction of the arch
without the need to install the temporary steel
towers. The main disadvantage of this option was that
the cables would have a smaller angle to the
horizontal, resulting in turn in great horizontal loads
on the pier that would have to be balanced.
Additionally, the complexity of the active anchorages
at the top of the piers would be greatly increased.
Something similar would also occur with the
foundations’ anchorages. This solution was then
conditioned by the maximum number of segments to
be built without an increase of the foundations’
anchors.
The optimal solution resulted in passing 6 pairs of
stays from the arch through the piers, which allowed
the casting 20 segments of each semi-arch before the
erection of the temporary steel towers and reducing
the construction time.
2.4. Provisional stay system
The stays’ active anchorages were located at either
the pier or the temporary steel towers. The passive
anchorages were located at the foundations and each
of the semi-arches.
The load applied to each stay could be changed as the
anchor was provided with a thread and nut system
and the length of the cable stay thus be reduced. The
application of tension as well as the decrease of the
loads during the construction process was always
developed at the active anchorages.
The system was provided with two of the four
possible barriers against corrosion defined for
permanent cables, so durability was guaranteed while
the construction lasted. It also provided thermal
insulation which helps to reduce the movements of
the semi-arches due to temperature variations.
Substitution of any of the strands of the cables was
allowed, should any break or fail. The design also
allowed the placement of additional strands once the
stay was loaded. Visual inspection of the stays was
always possible, so the integrity assured and any
abnormality during the execution period detected.
2.4.1 Anchorage in the arch
The anchorage of the cable stays in the arch was
achieved by using steel tubes that were left
embedded in the concrete during the casting of the
segment.
When the concrete of the segment had hardened,
they were completed from the outer side with a guide
tube with a smaller diameter, welded to the sheath
embedded, and which allowed the placement of the
deviator in its position.
To support the local stresses that
system transmits to the arch box,
locally increased in thicknesses, with
reinforcement so that the forces
transmitted.
the anchorage
the arch slabs
the appropriate
were correctly
Fig. 4: Auxiliary steel structure for cable ducts
Photo: Hector Faúndez
4/2016