Lafarge - Villa Navarra

THE LINE OF EFFORT
The module is formed by a panel
whose design matches the distribution
of effort in the structure.
THE DESIGN
The design produces optimal
mechanics, which recalls the design
of steel profiles.
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“Ductal®, as a
new material,
challenges
all the usual
methods of
calculation.”
VILLA
NAVARRA
Heat expansion is by far the most difficult to predict. The
highest expansion recorded due to variations in temperature
can be as much as 5 mm and, when the calculations give a
theoretically doubled value, as much as one centimetre. Ductal®,
as a new material, challenges all the usual methods of calculation.
The delicate lines made possible by the material mean that
the engineer must ask himself all manner of questions never
heard of with buildings in traditional concrete, particularly
questions about expansion and twisting. “The calculations
themselves are ordinary” says Mouloud Behloul, “but it’s the
approach that is not, above all for concrete.” The thickness of
the slab to resolve the problem of twisting has been measured
at 35 mm, “a sheet of paper in terms of concrete!
Originally designed for post-stressing, the panels would not
have been very different, apart from necessarily being firmly
anchored, as dictated by post-stressing. Entirely made of UHPFC
Ductal® and reliant on this one type of material (except for the
fixed reinforcing which was eventually placed in the ribs), the
panels lie in a more traditional fashion on two longitudinal
beams, placed 1.50 metre apart, forming a technical gallery.
Supporting braces, made up of a rod inserted in a socket
injected with resin and bolted at the surface with a wing nut
holding in place a load spreading plate, are placed along the
back beam. For the second beam, simple neoprene cushions
form the support.
PREFABRICATION
The art of
moulds
and pouring
This choice, apart from the experimentation with
materials that it affords, corresponds to a conscious
choice of building method. Rudy Ricciotti is enthusiastic
about the combination of a high tech product, as represented
by Ductal® and industrial prefabrication, with traditional
fitting without the constraints of the sophisticated processes
necessitated by pre-stressing. If the formulation of Ductal®
belongs to the world of the very latest highly sophisticated
technology, its use is gradually becoming less dependent on
laboratory culture, becoming known for real operational performance
on the bulding site. Traditional fitting gives this innovative
product, the result of ten years of research, a shared and
mass appeal, which finally allows one to foresee mass usage in
the short term. This “schizophrenic” relationship between
production and fitting fuels the architect’s hope of seeing this
family of concretes quickly becoming a material used by masons.
The first stage in the process, prefabrication, still relies
on the experimental culture necessitated by the material.
The theory is already tainted by empiricism, having benefited
from the expertise of the precaster, namely the Bonna Sabla
company, located near Montpellier, France. The production of
the mould and the method of pouring are determining factors
for the production of these parts with elaborate and complex
shapes, which also have a finished surface. The technological
requirements are satisfied by the metal moulds which are
produced by an aeronautics industry supplier. “In this way, two
different industrial worlds, which normally are not aware of
each other, are brought together in the manufacturing process,”
notes the architect.
TECHNOLOGICAL REQUIREMENTS
The manufacture of the metallic
moulds was performed by a supplier
from the aeronautical industry.
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