In the construction of the three central spans over
the arch, the clashes of the two Overhead MSS have
been necessary to solve. These interferences have
been solved by means of the partial disassembling
of the two gantries, reducing their length without
affecting their stability. The central span has been
built with only one overhead gantry, pulling the other
one back, being necessary the performance
of a closure operation similar to the one conducted in
the arch in order to avoid the cracking in last span.
4.
INSTRUMENTATION AND MONITORING OF THE
BRIDGE
A bridge with such a complex construction process
requires an exhaustive control of several parameters
to know exactly how the bridge is behaving at
any moment, structurally talking, but most intensely
during cantilever construction. For this reason
the bridge was instrumented throughout its
construction.
The data continuously recorded by the sensors were
transmitted to a website where real time and historic
information could be displayed.
In addition, each sensor was programmed to
immediately send an alarm signal to the site
supervisors’ cell phones when a given threshold value
was exceeded.
Four different types of sensors were used:
a. Geometric monitoring: Targets and prisms on
the arch, piers and provisional towers.
Clinometer on piers and towers were also
disposed.
b. Environmental
monitoring:
Concrete
temperature in arch, piers 6 and 15 and
provisional piers and temperature in stay cables.
A weather station was also positioned to monitor
ambient temperature, humidity, wind, etc…
c. Stress monitoring: Strain gauges on stay cables,
on reinforcing steel of the arch and on
provisional towers and also load cells on ground
anchors.
d. Terrain movement monitoring: Strain gauges on
arch foundations to monitor settlements.
5.
CONCLUSIONS
Er ecting an arch of this scale, overcoming the world
record span of a railway arch bridge in more than
110 m, for a structure in which the structural scheme
during construction differs widely from its in-service
functionality is a complex endeavor. Every single
element has required a deeply study, because
of being out of scale of what have been constructed
until now.
The construction of the bridge has been conducted by
FCC and the extra detailing and designing required to
address this complexity were performed by FCC’s
Engineering Department, which also provided
worksite support. The authors of the design verified
all the work performed in this stage of the project,
ensuring full cooperation among all the agents
involved.
Fig 10. Instrumentation of the bridge during its construction
4/2016