Page 57 - samyn_ebook2

55
Study of artificial lighting.
Artificial lighting is used to simulate the atmosphere created by natural daylight
entry. The artificial lighting study has taken the following principal criteria into
account:
- The main illumination under the covered areas of the platforms and tracks
has to be as homogeneous as possible.
- The minimum lighting level at the platforms is 50 lux, whether they are
covered or not.
- The lighting installation may not in any way blind travelers or train
conductors.
- The spaces reserved for travelers should be kept open and free from lighting
poles in the covered areas.
Given these criteria, a choice is made for a general indirect lighting system making
maximum use of the reflection against the arch formed coverings. Based on various
calculations and simulations, the desired level of indirect lighting is obtained by
placing projectors underneath the vaults on the four-legged supports.
Problems arise because of the large distance between the supports (39 m and 52 m),
because of the maximum height of the covering limited to 14 m above platform
level, and also because the vaults are situated above the tracks and not above the
platforms.
The final solution for the two central vaults of 39 m comprises 2 times 2 projectors
of 1,000 w located on either side of the four-legged supports. The two projectors
illuminate the vaults to the left and the right obliquely. For an arch measuring 39 m
per platform, 4 projectors of 1,000 w each are needed. (page 57)
An additional 400 w projector is added to each 1,000 w projector on the exterior vaults
spanning 52 m. This additional projector illuminates the area closest to the supporting
columns. To guarantee sufficient reach, high pressure lamps type HPI-T of 400 w and
1,000 w are selected.
Despite the variable height of the reflective vaults which can range up to 14m above
platform level, the obtained results are as follows:
- The exterior train track at the centre of the 52 m arches and the lateral tracks,
indicate an illumination level which varies between 78 and 121 lux at track level,
or an average illumination of 102 lux with 64 to 75% homogeneity.
- The interior train tracks at the centre of the 52 m arches and the lateral tracks,
indicate an illumination level which varies between 94 and 164 lux at track
level, or an average illumination of 128 lux with 48 to 65% homogeneity.
- The interior platforms at the centre of the 39 m arches and in axial position
indicate an illumination level which varies between 81 and 121 lux at platform
level, or an average illumination of 100 lux with 56 to 69% homogeneity.
Canopies are placed on the lower parts of the four-legged supports above the glass
boxes. These canopies are only slightly illuminated by the light projected overhead. To
literally highlight their presence, they are fitted with appropriate lighting equipment
with an average lighting level of 135 lux.
The illumination of the glass elevator openings makes vertical light marks within the
overall lighting of the vaults. To the right of these openings, the footbridge which
crosses the tracks from one side to the other is mainly illuminated by the lighting
on the central and lateral handrails. The overall effect is one of lightness but also
security.