4. ANALYSIS OF THE STRUCTURE
4.1 Computer analysis
The static and dynamic structural analyses carried out
for this project would require a specific article of its
own, due to its extent and complexity. As a brief
summary, it can be said that an advanced incremental
structural model, including every stage of the
construction, was developed for the analytical
calculation of the bridge (Fig. 9). In addition to the
influence of erection in the final situation, analysis has
also considered geometrical imperfections for every
stage and the effects of creep and shrinkage of
concrete, as well as material non-linearity both for
concrete and steel (using the true tensile stress-strain
curves and taking cracking into account).
The final shape of the arch was determined through a
step-iterative procedure, simultaneous to the
geometrical adjustments of the different crosssections, in order to achieve an essentially antifunicular configuration of the HSR loads (which
require a considerably different approach compared
to the road bridges), with continuous curvature where
the spandrel columns are located.
The arch stability was thoroughly verified for all the
critical loading combinations (with a different model
for each one of them), making a geometry-andmaterial nonlinear analysis, and using step-iterative
techniques. An initial pre-deformation with the shape
of the first vibration mode (which is an in-plane one)
was considered. Additionally, a sensitivity analysis with
different pre-deformation values was carried out and
stability under other deformed geometries was also
checked.
Ten different HSR load models, with speeds between
20 to 420 km/h, have been used to evaluate the
dynamic behaviour of the finished bridge.
In order to guarantee durability and to avoid dynamic
amplifications due to stiffness losses, the criteria of
not allowing cracking in the arch in SLS, both during
construction and under work-life loads, was
established.
Fig. 9: Structural analysis model for incremental geometry-and-material
nonlinear analysis taking into account construction phases
4/2016