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Precast technology
For The Pinnacle@Duxton, conscientious
efforts were made by the architects and
engineers to make the project buildable,
through the adoption of modularisation
and standardisation concepts. The
various options for the standard layouts
(S1 and S2) of the units in the residential
blocks, were obtained by configuring
units as mirror images of one another
and by rotation of these unit plans.
The modularisation of the units was
replicated to obtain the block design.
The floor plans for a typical storey
were also repeated for better efficiency
in precast construction. The adoption
of modularisation and standardisation
also enabled prefabrication to be costeffective
due to the high repetition of the
precast components and prefabricated
reinforcement.
As a result, it was possible to
incorporate a high proportion (about
85% of the total volume of concrete) of
precast technology in the construction
of the tower blocks. Precast components
were utilised for various elements
including prestressed plank, column,
lift wall, household shelter wall, gable
end wall, façade wall with bay window,
façade wall with planters, façade wall
with balcony, screen wall, refuse chute,
staircase, and parapet.
The use of large volumes of precast
concrete in the project increased
productivity by about 15%. In addition,
it facilitated construction works in a
tight, built-up, working environment,
and reduced environmental impact on
the existing area. In addition, precast
concrete elements are of better quality as
they are produced in a factory-controlled
environment.
To expedite construction works, a
typical floor was divided into two segments
(part A and part B) by a construction
joint (Fig 4). The construction work
was staggered, that is, a team of workers
from a construction trade would work
on part A and then move on to part B
without having to stop for workers from
the other trades to complete their tasks.
With this, it was possible to achieve the
anticipated 6-day construction cycle for
each segment of a typical floor.
The project team adopted the use of
large precast facade panels, measuring
about 7 m in length (Fig 5) compared
to the usual length of 3 m to 4 m. This
enhanced tower crane utilisation and
improved site productivity. The façades
of planter boxes, sun-shaded louvred
windows, and balconies, are arranged in
different combinations, creating a series
of vertical, zigzag lines that resemble
Fig 4: Typical fl oor layout showing the construction joint which divides the fl oor into two segments.
Fig 5: Large precast façade panels.
Fig 6: Precast, volumetric hollow-cored wall.
flowing water. In addition, the window
frames were fixed to the facades before
delivery to site. This will eliminate water
seepage through the windows. The wall
panels were designed to be hollow-cored
(Fig 6) so as to reduce the weight of the
components and minimise risk during
hoisting and erection.
THE SINGAPORE ENGINEER Jun 2010 · 13