Inspirations in Engineering 2013 - page 20

Nomination Category 1: Buildings
Project description
General hospital AZ Alma has commissioned a new
regional hospital, to optimise its functions and services.
Presently, the hospital still provides its services at two
other locations. These locations will be given a new
purpose once the hospital services have moved to the
new location, foreseen for 2017.
The new hospital will count 512 beds, to be housed in
two T-shaped wings, consisting of seven floors each,
with a total area of 55,000 m². They will be connected
by a central glazed atrium with ‘panoramic’ lifts. The
hospital will employ 110 doctors and 1,200 co-workers.
Besides the general services of a regional hospital,
it will also boast a spacious polyclinic, a day clinic, a
rehabilitation department and a dialysis department.
Next to the hospital there will be two new car parks for
staff and visitors, offering more than 1,000 places.
The central atrium will contain a whole range of
communal functions, including a reception area,
registration, a newspaper and magazines outlet, a
restaurant, sitting areas and greenery.
Glazed atrium
The central glazed atrium between the hospital
wings consists of a steel structure. Due to the large
dimensions of the hospital, dilatation joints are foreseen
between the atrium and the hospital wings. All beams
and columns of the atrium have different angles which
were sketched by the architects. This results in a
random load bearing structure in both the façades and
roof. The atrium measures 66 m by 28 m and is 28 m
high. At the front side of the atrium, there are eight
elevator shafts and two staircases, linked by post-
tensioned concrete beams on each level. At the rear
side of the atrium, four footbridges with a length of 28 m
form the link between the two hospital wings.
The roof consists of primary beams HEB650 – spanning
21 m – and secondary beams. The primary beams are
supported by two large trusses with a span of 42 m. As
a matter of fact, the truss is a mixture of a triangular and
a Vierendeel truss. It is supported by the rear façade
and one of the elevator shafts.
The horizontal stability is assured by both the concrete
shafts and the steel façades. The façades are therefore
considered as a bracing mixture of a triangular and
a Vierendeel. They consist of steel beams HEA300
and HEA500. The front façade (21 m by 28 m) is
horizontally (perpendicular on the façade) at six points
supported by the elevator shafts. The footbridges at
the rear side of the atrium hang as a balcony on the
rear façade, which results in moments and horizontal
forces perpendicular on the façade. The rear façade is
horizontally (perpendicular on the façade) supported
by the footbridges which act as horizontal wind bracing
Modelling and calculation
For the structural analysis of the glazed atrium,
Scia Engineer was used. Both the steel structure
and the concrete shafts were modelled. The main
challenge was to limit the deformations of the roof,
the main trusses and the different façades according
to the allowable deflections for the glass panels.
There is a mobile bridge between the main trusses
– for maintenance of the glazed roof – which results
in additional severe limitations for the deflection of
the main trusses. Scia Engineer was used for the
optimisation of the steel structure, in the function of
allowable deflections and strength. Concrete shafts
were modelled to evaluate the collaboration of the
vertical steel bracing in the façades and the concrete
The Scia Engineer model is also being used by the
contractor to calculate all the steel connections and in
making his montage study. Therefore different mounting
stages and additional load cases will be added to the
model by the contractor in the function of the mounting
sequence. Due to the montage of the steel structure, the
reactions on the foundations need to be re-evaluated.
Thanks to the fact that Scia Engineer has been widely
used, it is possible to use one global calculation model
from both the contractor and the main design engineer.
Software: Scia Engineer
General Hospital Alma - Eeklo, Belgium
Nomination Category 1: Buildings
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