bring compression forces in the concrete.
Under this
core there are vibro combination piles which are a
combination of a cast in place (in ground) pile with
a prestressed prefab concrete pile. The prefab pile is
stiff as well under tension loads.
Because the foundation of the tower lies next to the
harbour there are structural elements needed to
keep it in place.
A steel sheetpile wall together with
bracings are bearing the horizontal loads on the
tower.
Stiffness of the floors
The floors form diaphragms that carry the
wind
loads to the cores.
Diagonals in the floor plane
model these floors.
We have recalculated the forces
in these diagonals to determine the wind forces in
the steel frame and the concrete floors.
The ESA-Prima Win Model
The entire structure is modelled as a 3d model in
ESA-Prima
Win. The steel structure, the concrete
structure and the foundation are all designed and
engineered in one model.
With this model
we have
made different checks and investigated several alter-
natives. The different checks are described in this
chapter.
3 Dimensional rendering
The 3d rendering allowed us to show the ideas for
the structure to the different parties in the design
process.
With the pictures that ESA-Prima Win pro-
vided we were able to make clear the philosophy of
the structure and the consequences of different
alternatives.
Load combinations
As stated before, the tower balances on the big XX
columns. Therefore the vertical loads that work on
the structure are divided in three parts.
One part (of
the loads) in the cantilever, one part in the bridge
above the street and one part above the concrete
core. Beside the vertical loads,
wind loads are also
present on the building in four directions. In the
Dutch building codes we use four load factors: 1,2
and 1,35 for the dead loads, 1,5 for the live loads
and 0,9 for the beneficiary working dead loads.
With
these load factors we have made a selection of the
possible combinations.
We have worked out 20 load
combinations for the ultimate limit state and 15 load
combinations for the serviceability limit state.
Steel code check
The steel parts are checked with the embedded steel
code check of ESA-Prima Win. This check helped to
engineer different alternatives during the design
process.
With the weight data that ESA-Prima Win
gave
we
were able to estimate the costs for the
structure very quickly.
Pile foundation
The pile foundation is an integral part of the structur-
al
model. The flexible supports are put under the
foundation of the XX columns and the concrete
core. To investigate the long time effects of creep we
used the same model.
We just adapted the flexible
supports to the smaller stiffness.
2nd order calculation
To investigate the second order behaviour of the
structure
we have used the three dimensional
model.
With the model
we could analyse the behav-
iour of the structure under horizontal loads and the
increase of deformations due to the vertical loads.
Dynamic behaviour
Since the tower has a particular shape and slender-
ness the dynamic behaviour of the tower is very
interesting. To make sure that the accelerations are
beneath an acceptable level
we have used the
dynamics tool in ESA-Prima
Win. ESA-Prima
Win
determined the lowest Eigenfrequencies. These
Eigenvalues gave a good idea of the natural flexibil-
ity of the structure.
With the Eigenfrequencies we
could calculate the accelerations of the tower and
make sure the comfort for occupants was guaran-
teed.
Shortlist
Location
:
Terwenakker,
Rotterdam,
The
Netherlands
Height
: 80 metres from street level to the highest
point
Width
: 30 metres north - south44 metres east -
west
Storeys
: 22 storeys and one basement
Used steel
: approximately 1000 tons of high grade
steel S460
Cubic metres concrete
: 2.500 m³
Floor area
: 12.000 m²
Number of apartments
: 12 to 36 (depending on
the size)
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