The research project is based on energy-saving efforts,
which for their part can be carried through reducing e.g.
thermal losses through the wall. The need for developing
the facade elements was created, moreover, by changes in
the house building sector, with a shift in emphasis on
small house construction and with requirements for more
attractive outward appearance.
This research tends to examine the wall structure as an
independent structural entity by studying the possibility
of developing the wall structure and means of making it
competitive. An improved heat economy will also cause
changes in other properties of the wall.
The properties of the most commonly used insulating
materials such as mineral wool, polystyrene and
polyurethane, and their possible use as insulation in
concrete facade elements are also studied. Along with the
traditional mineral wool insulation, the plastics
insulation make new applications possible in certain
areas, for example, in cases where the thickness of the
concrete wythe and the number of wall ties can be reduced
by turning to advantage the strength of plastics
The interaction between the concrete wythes influences
the carrying capacity of the load-bearing facade element.
Depending on the wall ties, the interaction between the
wythes can be complete, partial or nil. The best carrying
capacity is attainable with a complete interaction, which
is produced e.g. by the diagonal truss reinforcement used
as wall ties. The diagonal reinforcement induces,
however, cold bridges and indirect forces between the
wythes. Therefore more flexible anchoring methods are
recommended when the sufficient carrying capacity is
achieved by them.
The purpose of anchoring between the inner and outer
concrete layer of the non-bearing element is generally to
suspend only the outer layer from the inner layer. It is
then advisable to try to arrange the anchoring as
flexible as possible, in which case the indirect forces,
as well as cracks and deflections induced through these
forces can be avoided. The outer layer can also be
suspended either partially or completely by means of
plastics insulation, when the strength and deformation
capacity of the bond between the insulation and the
concrete, and those of the insulation, together with the
long-term durability of anchoring are ensured.
The carrying capacity of the element and the size of the
indirect forces due to temperature differences with
different types of truss reinforcement were evaluated by
means of computer calculations. The strength of truss
reinforcement was examined further in laboratory tests,
in which the outer wythe of the element was loaded.
The external concrete wall is basically of compact
structure, but with regard to the heat economy and
moisture conditions of the structure it is important that
the joints and seams are also tight. On the other hand,
by ventilating heat insulation care is taken that the
moisture in the structure can escape outdoors.
Instructions for design, manufacture and assembly are
given in the report, by means of which these requirements
can be fulfilled.
The development of manufacturing techniques is possible
by applying prestressing and sliding form construction
techniques, fibre concrete and vacuum concrete
techniques, together with the sprayed insulating
materials and pastes. The above methods require, however,
that standardized products and large manufacturing series
In the report, a number of ideas of developing the
concrete facade element are proposed. Most favourably
judged were: the prestressed wall element of sliding-form
construction, the element based on the bearing capacity
of plastics insulation and connecting pins, and the
element provided with the concentrated anchoring. Bearing
capacity, manufacturing techniques and costs of new
structures are also discussed.
|Place of Publication||Espoo|
|Publisher||VTT Technical Research Centre of Finland|
|Number of pages||166|
|Publication status||Published - 1984|
|MoE publication type||D4 Published development or research report or study|
|Series||Valtion teknillinen tutkimuskeskus. Tutkimuksia - Research Reports|
- sandwich structures
- heat economy