2.4.2. Anchorage in foundations
A similar approach was taken for the design of the
foundations’ anchorages. The foundation has two
galleries on its sides so that the passive anchorage
might be accessed. The passive anchorage was placed
in a passing tube through the concrete section.
Foundations of P-10 and P-18 piers, adjacent to the
arch supports, received the first six pairs of cable
stays, the other end of the cable stays being in the
pier. Two other pairs of cable stays came from the
temporary steel towers. This caused a not negligible
difference in the angle of adjacent cable stays which
resulted in modifications of the geometry of the
foundation.
The passive and active anchorages were barely
different to those employed in post-tensioned
concrete.
2.4.3. Anchorage in concrete piers
The proposed solution had its difficulties. If we recall
that 6 type of cable stays will interact with the pier
and that each type has 4 cable stays, it is seen that a
total number of 24 cables were anchored to the pier.
12 of them provided support to the arch and 12 of
them balanced the horizontal loads on the pier by
being anchored to the foundation of the adjacent
pier.
Because of the high number of anchorages in the pier
and its reduced dimensions, a detailed tridimensional
model was developed to ensure that the solution was
viable.
The possibility of leaving embedded in the upper part
of the pier all the anchorages, with no interferences
between them, was verified. The real dimensions of
the tubes, which depend on the stay system, were
accounted for.
To avoid inappropriate concentrations of stresses in
the hollow concrete section, the part affected by the
anchorages is filled with concrete.
Due to the complexity of the assembly process of the
embedded sheaths in the pier, and because a high
level of accuracy was needed, a pre-assembly in the
workshop using an auxiliary steel structure was
undertaken. The accuracy of the assembly was thus
ensured and the steel structures transported to site.
These structures acted also as support of the
reinforcement of the pier and, with an operation
easily controlled by classical topography, the anchor
Fig. 5: Form traveler during casting
Photo: Luis Miguel Salazar
4/2016