2. CONTENT
1. Introduction
2. Concept
3. Structural design and behaviour
1. ETEF cushion
2. Cable net structure
3. Tripod
4. Construction
1. Eraction of tripod
2. Cable installation
3. ETEF cushion installation
5. Detail
6. Drawings
3. • Architect - Foster + Partners
• Engineer - Buro Happold
• Astana, the new capital of
Kazakhstan, is being constructed
in an austere eastern landscape
with an extreme climate.
• Its remote steppe location to the
north of the country
experiences temperature below
freezing for half the year with
extremes ranging from - 40ºC to
+40ºC.
1. INTRODUCTION
4. • Entertainment Center represents a major new civic, cultural and social venue for
the people of Astana, bringing together a wide range of activities within a
sheltered climatic envelope that provides a comfortable environment all year
round.
• The Kahn Shatyr (Big Tent) provides 100,000m2 of floor space where the people
of Astana can meet, shop and relax year round in comfort despite the extreme
environment.
6. • Creating a giant, free-spanning
enclosure with the minimum of
support.
• Single-masted cable net in a conical
form was their natural choice due to its
simplicity and efficiency of material.
• With a single compression mast to
lift the net and create a large volume
underneath, the roof skin is in tension
and can use cables rather than beams
to carry all loads.
• It also creates a very strong “iconic”
form on the skyline – a critical
consideration for such an important
building in the capital city.
2. INITIAL CONCEPT
7. • The 19,000m2 transparent
roof of the Entertainment
Centre comprises ETFE
(Ethylene tetra fluoroethylene)
cushions supported on a cable
net structure.
3. STRUCTURAL DESIGN
3.1 ETEF cushions
8. • The skin of ETFE cushions is very
lightweight and insulates while still
providing natural daylight.
• The cushions are flexible to accept
the large deflections of the cable
net, however their frames are much
more rigid, and so they decided a
staggered arrangement of
cushions.
• This allows the hoop frame of one
panel to squeeze in on the mid
point of the adjacent panel and
benifit from the inherent flexibility of
the cushion.
3.1 ETEF cushions
9. • Each tripod leg is formed from a three
chord truss with 1000mm diameter
circular hollow main sections, the back
leg resists 140MN while each front leg
resists 50MN.
• The legs meet at a hub which supports
12 pin ended struts reaching to the
cable net top ring.
• The hub is located so that its centre
line corresponds with the resultant
axial force from the cable net under
prestress loads.
3.2 Tripod Structure
10. • The roof cables are collected 90m
above ground on a ring at the top
of the steel tripod and span to the
sloped concrete perimeter which
forms the base of the building.
• The shape of the cable net is
based on a classic cone which has
been pulled over to one side.
• This gives the Entertainment
Centre its distinctive sloping
architectural form.
3.3 Cable Structure
Conceptual sketch by norman
foster
11. • Radial cables span from the top ring of the
steel compression mast to the outer
concrete perimeter and are prestressed
against hoop cables to form an anticlastic
surface.
• 192 pairs of 38mm diameter radial cables
vary in length from 125m at the front of the
tent to 70m at the back.
• The hoop cables are arranged perpendicular
to the ridge line of the radials.
• A relatively high prestress of about 80% of
the peak cable forces is utilised in the tent to
control deflections to around 800mm over
the longest cable span.
3.3 Cable Structure
12. • The tripod provides the single
point of support to the centre of the
cable net and is an important
element for the architecture of the
building.
• Traditionally the central support of
a conic tent is a single mast,
pinned at both the top and the
bottom and stabilised by the tent
that it supports.
• This only ever places axial force in
the mast which moves with the
tent under asymmetric loads and
reduces the peak tensions within
3.3 Cable Structure
13. • However, it was felt impractical to
temporarily support a fully articulated
150m high single mast during
construction so this principle was
adapted for the Entertainment Centre.
• The tripod structure which is used
provides a robust constructible base
while the articulated top ring that it
supports provides some movement to
relieve the forces in the cable net.
• The movable part of the mast is then a
much smaller element that was easier
to temporarily brace during
construction.
bracing
14. • The greatest challenge to overcome
in the construction process was the
erection of the tripod.
• The general arrangement of the
tripod was configured to allow a
dramatic single lift process where the
whole 1,700 ton tripod was pivoted
around pins at the bases of the two
front legs.
4. CONSTRUCTION
4.1 Erection Of Tripod
15. • Strand jacks, attached to the top of a
temporary tower in front of the tripod,
pulled on lifting cables attached to a frame
on the tripod hub.
• As the front legs pivoted up, the top of the
back leg lifted on a temporary pin
connection under the hub whilst its base
slid in on a bogey running on a rail track.
16. • Temporary bracing to the cable
ring remained in place until the
cables had been installed and
correctly prestressed.
• Although the tripod provided
the most dramatic sequence in
the construction of the Khan
Shatyr, the installation of the
cable net was also challenging.
• The radial cables were lifted
individually into a slack
condition with cable clamps
attached ready to accept the
hoop cables which were placed
over the top of the radials.
4.2 Cable Installation
17. • Once all the cables were in place
tension was pulled into them using a
jacking detail at the base of the radial
cables to bring the net into shape
and allow the installation of the
cushions to proceed.
• The ETFE cushions were slid into
their extrusions from the base and
pulled through to the top.
• The length of the cushions were
maximised to reduce their number
and make the installation as fast as
possible, but during the winter
months the cold temperatures made
the ETFE much harder to work and
4.3 ETEF Installation
