Inspired by the structure of the human DNA , the US$272-million Cayan Tower is twisted at 900 from top to bottom. Developed by Cayan Real Estate Investment and Development Company and designed by Chicago-based Skidmore Owings and Merrill (also the masterminds behind Burj Khalifa), the world’s tallest twisted tower has given engineering a new ‘high’.

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Cayan Tower, World’s tallest twisted tower
am quite into the idea
of engineering being
beautiful,” said Sean
Booth, and we cannot
disagree with him.
This statement seems to come to life
when you glance at Dubai’s Cayan
Tower, the world’s tallest twisted
tower. Developed by the Cayan Real
Estate Investment and Development,
the tower is designed by Skidmore,
Owings and Merrill SOM architectural
group—the same group that built the
Burj Khalifa in Dubai and the Trump
Tower in Chicago. The Cayan Tower,
inaugurated on June 10, 2013, is yet
another engineering marvel. But the
unusual form of the building presented
various challenges for its designers and
developers.
“In a distinctive application of
architectural expressions through
structural form, the Cayan Tower twists
a full 900
from its base to its crown 314
m (1,038 ft) above the ground, through
a series of incremental plan rotations at
each level. The dramatic architectural
form of the tower presented the multi-
disciplinary design team with unique
challenges that are not typically
encountered in the design process for
more conventional building structures,”
informs Ashraf Qudsiyeh, Engineer &
Project Manager, Cayan Real Estate
Investment & Development.
The efficiency, constructability
and overall viability of the tower
depended upon the ability of the
architects and engineers to develop
and implement simple, straightforward
building systems that work with the
geometrically complex building form.
To ensure clarity despite the glazing
sunrays while still responding to the
specific climatic conditions of the
Emirates, the glass is set back from
the face of the building, allowing
the recessed terraces, spandrels
and columns to act as passive solar
protection. Screens were added to
further shade the individual windows;
When
a creative
‘twist’
engineering gets
Inspired by the structure of the human DNA, the US$272-million Cayan Tower is
twisted at 900
from top to bottom. Developed by Cayan Real Estate Investment
and Development Company and designed by Chicago-based Skidmore Owings
and Merrill (also the masterminds behind Burj Khalifa), the world’s tallest
twisted tower has given engineering a new ‘high’.
Nishi Rath
“I

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Cayan Tower, World’s tallest twisted tower
1. No of storeys = 6 basements+ ground floors + mezzanine
+ 6 podiums + 64 residential floors
+ 2 mechanical floors + 6 floor steel structure
2. Total building height = 314.8 m (1,038 ft)
3. Area of plot = 3,160.83 sqm (34,024 sqft)
4. Total built-up area = 118,125.97 sqm (1,271,539 sqft)
5. Structural types = Super high-rise building club
6. Rotation degree = 900
(0.30
per metre height)
7. Contract value = Lump sum offer of 770,446,368 DHS
8. Gate level = (+3.50) DMD
9. Top level = (+306.365) DMD
10. Floor area ratio = 27.34
11. No of lifts = 7
12. No of shops/parking = 6 (11 cars)
13. No of studio = 17 (17 cars)
14. No of apartments > 1600 sqft = 91 (182 cars)
15. No of apartments < 1600 sqft = 404 (404 cars)
16. Total no of parking = 614 (cars)
17. Total net residential area = 64,887.21 sqm (698,463 sqft)
18. Total net commercial area = 1,329.89 sqm (14,315 sqft)
19. Total parking area = 24,328.19 sqm (261,875 sqft)
20. Total steel reinforcements grade 460 = 25,000 tonne
21. Total concrete grades (C-40, C85) = 77,000 m³ 320 kg steel/1 m³
22. Net area utilised per floor = 970 sqm
23. Total area/floors = 1,160 sqm
24. Concrete volume/floors = 440 m³ concrete
Quick facts
they were then scattered to create a
monolithic texture, reinforcing the
project’s powerful formal gesture. To
this, Qudsiyeh adds, “Near the top,
column cladding panels are gradually
replaced with perforated panels;
the quantity and size of the terraces
increases, thereby effectively dissolving
the tower into the infinite. Finally,
the tower body disappears and the last
levels of screens float past on nearly
invisible cables at the top of the tower.”
Structural System
The tower is founded upon a 3-m
thick reinforced concrete mat
foundation, which is supported by 99
1.2-m diameter bored, cast-in-place
reinforced concrete piles extending
approximately 30 m below the mat
foundation. The piles transfer
the tower loads to the sub-
grade, primarily through
perimeter skin friction.
The sub-grade consists
of loose sands
and sandstone
bands overlaying
cemented marine
deposits and
calcareous slit
l i m e s t o n e /
siltstone.
The lateral
load resisting
system for
the tower is a
combination of a
reinforced concrete
moment-resisting
perimeter column
& spandrel beam
frame action, which
takes 75% of the
lateral force. The
remaining 25% is
taken by a circular
central core wall,
connected at each
level by the two-way
spanning reinforced
concrete flat plate
slabs acting as
diaphragms. “This system maximises
the effective structural footprint of the
tower by utilising a significant amount
of the vertical reinforced concrete
for lateral load resistance,” informs
Qudsiyeh.
Design philosophy &
Standardisation
The tower’s design philosophy is based
upon the exterior form of the building
as a direct expression of the structural
framework. The engineers studied a
series of options for the perimeter
frame to create the tower’s unique
twisting geometry. Ultimately, it was
determined that there were distinct
advantages, from the standpoint of
architectural efficiency, structural
performance and ease of construction,
to stacking the columns in a step-
wise manner at each level, where each
column slopes in one direction, and
is offset over the column below, to
generate the twisting building form.
“For the Cayan Tower to be
realised as a viable structure, the
seemingly complex building form must
ultimately be derived from a structure
that is straightforward and efficient
to construct. The structure should
maintain practical and repetitive
architectural floor layouts. The system,
as described above, offers significant
construction simplification by
permitting a high level of
repetition in the formwork,
which directly impacts
the construction cycle
time,” adds Qudsiyeh.
Also, this
system leads to
residential floor
layouts, which
are repetitive
at each level
despite the
twisting nature
of the building
form. Six typical
floor layouts
were used, with
each residential
unit designed to
allow terraces to
exist in one of two
or three locations.
M e c h a n i c a l
systems, which are
normally housed
in risers that pass
vertically through
the building, do
not have such
a free-ranging
straight vertical
path in Cayan
Tower. “Although

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Cayan Tower, World’s tallest twisted tower
the floor below has the same area and
layout, the building’s twist dictates that
the demising walls are shifted about
1.30
, about the tower’s plan centre,
from level to level,” he states.
For the Cayan Tower, major
mechanical risers are located in the
circular central core, which allows a
straight vertical path through the
tower. The balance of the building’s
mechanical, electrical and plumbing
systems is located within a deep
demising wall between the central
circulation corridor and the residential
units. The zone is specifically located
and designed to create a minimally
obtrusive vertical path for the building
services to access all residential units
as they rotate about the central core
as the building ascends. As the typical
units and their entrance doors rotate,
they shift to new positions within the
corridor demising wall.
Similarly, the exterior wall was
designed with an emphasis on
standardised parts sized and fit
together to enclose bays that are not
identical. For example, the opening on
each bay is slightly larger or smaller
than the one next to it. To use exterior
wall units of the same size,
the joints were designed
to allow a slightly varied
relationship between
pieces. The spandrel caps,
which ring the building,
are deeper on one end of
each bay than they are at the other end
of the same bay, accommodating panel
adjustments for each bay’s geometric
conditions.
Qudsiyeh elaborates, “Because of
the building’s singular formal gesture,
the design team wanted to reduce
or minimise elements that distracted
from or contradicted the smoothness
of the twist. Two such elements were
the balconies and the stepped columns.
Each unit was required to have a
balcony, and with standard unit layouts,
the balconies initially stacked one on
top of another, thereby creating vertical
slots of deeper reveals in the façade. By
organising each standard unit to have
the flexibility to position its terraces
in one of two or three locations, the
designers gave themselves the freedom
to shift the terraces more randomly
along the façade and eliminate the
vertical stacking.”
Careful consideration was given
to the standardisation of the Cayan
Tower in order to limit the number of
unique conditions that would require
customisation, such that construction
could proceed as quickly and be as
straightforward as possible. “When
compared to a similar building taken
as a straight extrusion with height (no
twist), it is estimated that the twisting
form of the Cayan Tower reduced the
structure’s across-wind excitation by
around 25% or more,” he says.
Challenges faced
The idea was flagged in 2006, with
Cayan wanting an iconic design that
the world would talk about. And the
world indeed is … But the journey
was not smooth; the project comprised
seven years of construction and
received the certificate of completion
in May 2013. The main challenge
faced by the team was the collapse that
happened on February 7, 2007, which
delayed the project for two years. The
site was completely excavated, all piles
were driven and the full shoring system
was developed. “Due to the collapse of
the shoring system, the whole site was
totally flooded; the primary objective
was to separate the flooded site from
the bordering marina with a buffer
zone in an excess of 10-m width,”
Qudsiyeh explains.
To achieve this, a 12-m wide and
30-m long ‘coffer dam’ was constructed
to block the breached portion of the
shoring system (this is in combination
with stabilisation work of existing
structure). The second objective was
to discharge the water back into the
marina and simultaneously stabilise
the remaining yet much weaker and
vulnerable shoring system, which was
followed by an elaborate rectification
works to reinstate the original site
conditions that prevailed prior to the
collapse. Upon successful completion
of these measures, normal construction
work resumed. “There are different
theories explaining the reason(s) for
the collapse. All of these indicate that
the shoring system failed to counter
resist the applied earth and hydrostatic
pressures that arrived at their maximum
values when the excavation reached the
cut-off levels of the pile heads at 24 m
below the ground surface,” expresses
Qudsiyeh.
Machines and manpower create
a marvel
To construct this magnificent structure,
two tower cranes with a total height
equivalent to the full height of the
tower were utilised. One of the tower
cranes was positioned inside the tower,
while the other was positioned outside
the tower. The latter was
dismantled upon the whole
skeleton of the tower to
allow the installation of
the façade glazing and
cladding panels, while the
other was utilised until
completion of all work. A hydraulically
manoeuvred sliding form was utilised
for the construction of the cylindrical
core. At the peak, a workforce of
about 3,000 personnel was engaged
in construction, including labourers,
foremen, logistical staff, engineers,
consultants and experts from all four
corners of the globe. Cayan Tower
is an architectural vision, which is
not only poised to become the tall-
standing icon of Dubai but will also
serve as inspiration for engineers across
the globe.
nisi.rath@network18publishing.com
To ensure clarity despite the glazing sunrays while still
responding to the specific climatic conditions of the
Emirates, the glass is set back from the face of the building,
allowing the recessed terraces, spandrels and columns to act
as passive solar protection.