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The principle of concentrating compression and
distributing tension in order to create the lightest
possible structures is expressed in many forms in
the work of Philippe Samyn. A structure can be
very light and not give the appearance of being so,
such as the Eversite office building in Brussels
(01-368, figure 36)
. It consists of a seven-storey
cylinder resting on slender columns and linked to a
technical core at the back via bridges that trans-
mit a horizontal bracing effect.
The seven-storey cylinder, which looks quite heavy,
appears to be ‘levitating’, while the adjacent building
seems completely separate, although the compression
is passing through it. The exterior staircase rests on a
column and is braced at the core of each floor by two
tensioner bars. In the project for Leuven railway station
(01-389, figures 37)
, the goal was to make the material
visually disappear. The arches could have been solid,
but the non-essential material was removed and the
light vents absorb what remains. The exterior staircase
for the fire station in Enschede
(01-450, figures 38)
is
supported by two thin columns and braced by over-
hanging landings and ground-anchored vertical cables,
while the metal used is transparent enough to look like
fabric. In the project for the Tour Signal at La Défense
in Paris
(01-533, figure 39)
, the initial idea was to make
a hollow tower with no structural facade. The central
core is used as a vertical shaft for natural ventilation
and light wells; light is brought in by atriums in groups
of five floors, deployed in a winding manner around the
building. A bracing structure is also used on the outside
of the housing tower for the Sint-Amandscollege in
Concentrating
compression and
distributing tension
Kortrijk
(01-510, figure 40)
. The double-skin facade is
transparent and contains a terrace on every two floors
between the two skins. The bracing veils that border
these terraces are clad in wood. Inside the building, the
structure consists only of columns. In his designs, the
engineer is often ‘frightened’ by compression because
of the risk of buckling. In reality, according to Philippe
Samyn, ‘if one follows the rules, this illness can be
cured completely’ – a heavily loaded column will not
buckle if it is short enough. The advantage of compres-
sion is that the connection has a weight of zero (a sim-
ple superimposition of elements). On the other hand,
with tension, one can go all the way up to an element’s
maximum allowable constraint, but it must be solidly
anchored, and the consumption of the material used
for the anchor is directly proportional to the section of
the element. Moving from the bar (linear structure) to
the sheet (surface structure), the search for lightness
is also bound up with the means of assembly
(figure
41)
. While the buttonhole (a sheet perpendicular to the
bar, like a link in a bicycle chain) consumes a great deal
of energy, the seam (a sheet in the same plane as the
bar, which is wrapped around the end of the sheet and
attached to itself) consumes almost no energy at all.
The goal of structural lightness requires a small number
of columns that concentrate compression, while a large
number of long stretched elements distribute tension.
To transmit low loads over long distances by compres-
sion, Philippe Samyn uses braced columns, with sepa-
rating tie rods placed in a square or triangle
(figure 42)
.
One of the first applications of this principle is in the
exterior columns for one of the SmithKline Beecham
buildings in Rixensart
(01-317, figures 43)
. The goal
was not to limit the admissible load, but to determine
what structure would have the lowest overall weight.
A student at the
vub
, Chantal Buyl, perfected the exact
calculation method for a braced column with a single
tie rod. Jan Vansteirtegem’s PhD thesis studies the
optimum weight for multi-braced columns (with multi-
ple tie rods). This allowed Philippe Samyn to extend the
application to braced arches
(figure 44)
, which were
Figure 36: Eversite building,
Brussels (01-368)
Figure 37: Leuven railway station
(01-389)
Figure 45: First pedestrian footbridge
for Leuven railway station (01-415)
36
37