4.2 - VSL

In the end spans and in the central span, the
slabs are horizontal; in between, they have a
4.5% gradient in the longitudinal direction,
thus serving also as ramps. This form of
structure results in a separation over 2 x 4
spans along the longitudinal axis of each
floor.
The seven lower slabs are 200 mm thick.
They are designed for a live load of 2 kN/m 2
The loading of the roof slab is composed at a
maximum of the snow load of 11.5 kN/mz
and a roof garden of 4 kN/m 2 . The thickness
of the roof slab is therefore 250 to 400 mm.
The high loading also necessitated
strengthening at the column heads. It was
possible to dispense with expansion joints in
all the slabs.
Construction
Due to its high elevation, Saas-Fee has a
long winter season in which no construction
work is possible. In addition, sudden cold
spells and falls of snow must be expected in
spring and autumn. Only the period from the
end of May to the middle of October 1980
was therefore available for building the main
structure. This meant that on average one
half slab (area 1,450 m 2 ) together with the
associated columns and walls had to be
erected each week. Furthermore, due to
reasons associated with formwork and posttensioning,
the half slabs at the uphill side
always had to be two storeys in advance
(Fig. 107). Fig. 108 shows the construction
programme of two half slabs situated on
adjacent levels.
The required minimum concrete strength for
stressing was reached normally three days
after concreting. One half slab could
therefore be fully stressed each Tuesday and
the formwork then stripped from it.
Post-tensioning
The slabs were designed on the principles
for unbonded post-tensioning set out in
this document. The monostrands used are of
nominal diameter 15 mm (0.6"), have a
cross-section of 146 mm 2
and an ultimate
strength of 257.8 kN. 50% of the tendons are
located in the column lines, 50% in the span.
Some of the tendons over the columns are
formed into bundles of two.
In the longitudinal direction, the strands were
divided by a non-stressed inter-media
Figure 103: The car park during construction
Figure 104: Plan
Figure 105: Longitudinal section
Figure 106: Cross-section Figure 107: View during construction
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