Page 69 - Between light and shade

Light, transparency and reflection

the other hand (0.2 to 0.3 kN/m² for the glazing,
and then 0.3 to 0.7 kN/m² for the structure. i.e. a
vertical force of 0.5 to 1 kN/m²).

Compelled by stiffness 67, structures are still
frequently made from ordinary steel S235 68 as
in the following examples. However, the use of
ultra high-strength steel, long reserved for cables
and now available in thin sheets (supported by
the automotive industry!), is an absolute must
for reducing the quantity of material. It involves
replacing stiff glass with flexible membranes and
results in new structural morphologies, on which
I am currently working.

The canopy of the Comptoir forestier in
Marche-en-Famenne 69[01/279, Fig. 63 to 65] made
up of single trapezoidal panes with a reflec-
tive coating, forms a torus section (K > 0) on a
wooden framework.

67 The modulus of elasticity E (which determines the stiffness
of a material and is expressed in Pascals (Pa), or N/m²) is E =
210 GN/m² for steel, whatever its yield strength, and which
varies from 235 MN/m² for mild steel to 2000 MN/m² for ultra
high-strength steel.
68 The “strength” σ of a steel is expressed as a capital S followed by
its yield strength in MPa (stress at which it stops being defor-
med elastically). It is currently possible to obtain sheets that are
between 1 and 12 mm thick in S2000, and which are perfectly
weldable.
69 Bulletin of the International Association for Shell and Spatial

Structures, vol. 36 (1998), no. 2, August 118, pp. 73-82. Available
as “01/279” at www.samynandpartners.be.

69