Basic HTML Version
82
used in particular in the second design for the pedes-
trian footbridge at Leuven railway station
(01-415, fig-
ures 44)
. The first footbridge for Leuven railway station
(01-415, figure 45)
was held up by braced columns. Its
structure was so light that the first ten modes of vibra-
tion had natural frequencies of less than 1 Hz, making it
very sensitive to dynamic effects.
23
In order to avoid uncomfortable – even hazardous
– movement in windy weather, a static aeraulic damp-
ing system was put in place, using sheets of metal
deployed as railings: air passing through the perfora-
tions in the metal dissipates motion energy via viscous
friction, while the perforations themselves contribute
to equalising pressure on both sides of the deck, which
reduces the dynamic action of the wind. Vibrations may
also be generated by resonance caused by the move-
ments of crowds of pedestrians. To dampen them, the
walkway was fitted with an intelligent device: a piezo-
electric actuator stretches or shrinks under the effect
of an electric current triggered by the measurement
of movements, in such a way as to counter vibrations
generated by crowds. If the device fails and requires
repair, the bridge is uncomfortable but still usable. In
the initial project for the footbridge, Philippe Samyn
increased the number of small welded bars in order to
alleviate the problem of buckling instability. The bars
intertwine to create very light, low-energy-consumption
ensembles that better occupy the available volume,
given the space needed for pedestrians
(01-415, fig-
ure 45)
. In the project to renovate the former medical
school at Porte de Hal, Brussels
(01-239)
, as well as
for the Campidoglio Due in Rome
(01-526, figure 46)
,
Samyn uses large, low-loaded columns supported by
cabling that links them together. For the extension
of the Euro Space Center at Transinne, in the town
of Libin
(01-518, figure 47)
, which was delivered in
October 2008, a network of 4-mm cables reduces the
buckling in an almost invisible fashion. The same princi-
ple was applied to the facade of the
ulb
medical school
auditorium in Anderlecht
(01-270, figure 48)
, which
was created in
ipe
80 profiled steel supported
by barely visible cabling.
37
Figure 37: Leuven railway station (01-389)