advanced building skins 14 | 15 June 2012 - lamp.tugraz.at - Graz ...

Advanced Building Skins
correspond to a lightweight concrete or even wood or aerated concrete. Fulfilling the load bearing
functionality could possibly lead to an increase in density or thickness, but even so the thermal and fire
retention properties would not be resolved.
Thermal insulation and fire retention
A material that is a poor conductor and is not highly combustible satisfies the functionality of thermal
insulation but not that of fire retention. By increasing the thickness, it is possible to improve the
response to the latter by slowing its loss of integrity.
In this case, the thickness is conditioned by fire retention and not by thermal insulation.
If a material is sufficiently conductive, the thickness required to provide thermal insulation will surely
be greater than that needed to avoid fire propagation.
For instance, the combustion speed (0.76 mm/min) of KLH plywood requires the use of a 117-mmthick
panel to satisfy the fire retention property. This thickness is increased to 200 mm to fulfill the
required transmittance.
This same thickness of aerated concrete is capable of withstanding fire for six hours but it barely is
able to fulfill the transmittance required in the harshest climatic zone, E1.
In combustible materials of a thermal conductivity of around 0.035 W/mK, that is, all those thermal
insulators not included in category A1, the increase in thickness is justified by the materials’ satisfying
fire retention requirements.
In a steel sandwich panel with a polyisocyanurate (Polyiso) core, less thickness is required to satisfy
the thermal functionality (80 mm) than for satisfying the needs for fire retention (175 mm).
The combination of separating these two functionalities from the panel gives rise to the definition of
two types that each fulfill four functionalities, depending on whether the fourth functionality included
is that of thermal insulation or fire retention, respectively.
5 The Morphological Diversity of Load-bearing Inner Skins of Panels
5.1 Morphologies Definition
There are six alternate morphologies, distinguished by two characteristics: geometry and structure.
The first of these focuses on the external shape of the panel, while the second contemplates alterations
to the thickness of the section. If the sheets that make up the panel have been cut in opposite directions
(transversally or longitudinally), the result will be different sections and a heterogeneous plate.
SECTION
GEOMETRY
Rectangular
Table 1: Morphological possibilities
STRUCTURE MORPHOLOGY
Homogeneous Homogeneous
Heterogeneous
- 7 -
Sandwich
Hollow
Non-rectangular Heterogeneous Ribbed
Nervate
Stud
5.2 Morphological Alternatives per Each Functional Type
When changing from a rectangular geometry to a corrugated, ribbed or framework panel, the panel
will lose functionalities. Obviously, this is the case whenever one maintains a thickness that is not
excessive for a ribbed or corrugated panel.
Panels that have a constant transversal section throughout their width and length typically display a
better behavior as they always react in the same way to incidents. They are typically suitable for
satisfying many functions.