Tube structures and its type with comparison .

• What is mean by tube ?
• Concept of tube structure.
• Types of tube structure
• Comparison
What We Are Going To Learn

• The systems which resist lateral loads on a
building is designed to act like a three-
dimensional hollow tube.
• Can be constructed using steel, concrete, or
composite construction.
• It can be used for office, apartment and mixed-
use buildings. Mostly buildings with 40+ stories
What is mean by tube ?

• A building can be designed to resist lateral loads
by designing it as a hollow cantilever
perpendicular to the ground.
• In the simplest incarnation of the tube, the
perimeter of the exterior consists of closely
spaced columns that are tied together with deep
beams through moment connections.
• This assembly of columns and beams forms a
rigid frame.
Concept of tube structure

• This exterior framing resist all lateral loads on
the building, thereby allowing the interior of
the building to be simply framed for gravity
loads.
• Interior columns are comparatively few and
located at the core.
• The distance between the exterior and the core
frames is spanned with beams or trusses.
• This maximizes the effectiveness of the
perimeter tube by transferring some of the
gravity loads within the structure to it and
increases its ability to resist overturning due to
lateral loads.

Examples of Tube structures
DeWitt-Chestnut apartment
building, Chicago 1965
John Hancock Center 1969

Examples of Tube structures
Jin Mao Tower, Shanghai
1998
Burj Khalifa, Dubai
2010

• Framed tube system
• Tube -in a tube system
• Bundled tube system
• Braced tube system
Types of Tube structures

Framed tube system
• Closely spaced perimeter columns
interconnected by beams.
• It can take a variety of floor plan shapes from
square and rectangular, circular.
• Most notable examples are the Aon Center and
the destroyed World Trade Center towers.

Framed tube system
• Closely spaced perimeter columns interconnected
by deep spandrels.
• Whole building works as a huge vertical cantilever
to resist overturning moments.
• Exterior tube carries all the lateral loading.
• Gravity loading is shared between the tube and
the interior columns or walls, if they exist.

• If the tube loaded on side AB, then the whole frames AB and CD are
called ‘Flange frames’ and the frames AD and BC are called ‘Web frame’
Cont…
Shear lag

• The forces in the web frame are growing smaller toward
the center linearly instead in Fig(b) this phenomenon is
called Shear lag.
• The ratio of the stress at the center column to the stress at
the corner column is defined as ‘Shear-lag factor’.
• Stress distribution of the flange and web column - opposite
sides of the neutral axis are subjected to tensile and
compressive forces - under lateral load - Fig. (b)
• The prime action is the flexibility of the spandrel beams
that produces a shear lag that will increases the stresses in
the corner column and reduces those in the inner columns
of both the flange panels AB and DC and the web panels
AD and BC

Tube in a tube system
• An outer framed tube together with an internal elevator
and service core.
• The outer and inner tubes act jointly in resisting both
gravity and lateral loading in steel-framed buildings.
• The bending and transverse shears are supported three-
dimensionally at the flange and web surface in the
structure.

Proportioning:
• 30m minimum floor dimension
• Centrally stability core around
lifts/stairs, moment frame around
perimeter
• 30 to 60 floor, 100 to 160m height
• Clear floor plates, but wide perimeter
columns and deep perimeter beam
constrains view
• Traditionally 2 or 3 zone elevator
arrangement, but would benefit from
optimization using double decks or sky
lobbies.

Behavior of Tube in Tube Tall Building
• Respond as a unit to lateral forces
• The reaction to wind is similar to
that of a frame and shear wall
structure
• The wall deflects in a flexural mode
with concavity downwind and
maximum slope at the top, while the
frame deflect in a shear mode with
concavity upwind and maximum
slope at the base
• Composite structure - flexural
profile in the lower part and shear
profile in the upper part.The axial
forces cause the wall to restrain the
frame near the base and the frames
to restrain the wall at the top

• The deflection & wall moment curve indicate the reversal in
curvature with a point of inflexion
• Fig-c - The shear is uniform over the height of the frame, except
near the base where it reduces to a negligible amount
• At the top, (where the external shear is zero), the frame is subjected
to a significant positive shear - balanced by an equal negative shear
at top of the wall, with a corresponding concentrated interaction
force acting between the frame and the wall.

Advantages:
Cont…
• More resistance to overturning moments.
• Core framing leads to a significant gain in rentable space.
• Identical framing for all which are no subjected to varying
internal forces due to lateral loads.
• The final analysis and design of the tube can proceed
unaffected by the lengthy process of resolving detail layout and
service requirements in the core area.

Bundled tube
• Instead of one tube, several tubes are tied together
to resist the lateral forces.
• The bundle tube design was not only highly efficient
in economic terms, but it was also innovative in its
potential for versatile formulation of architectural.
• The bundled tube structure meant that "buildings
no longer need be boxlike in appearance they could
become sculpture."

• It is a cluster of individual tubes connected
together to act as a single unit
• Maintain a reasonable slenderness (i.e., height-to-
width) ratio – Neither excessively flexible and nor
sway too much
• Cross walls or cross frames – increases three-
dimensional response of the structure.
• Individual tubes could be of different shapes, such
as rectangular, triangular or hexagonal as is
demonstrated by this building

Diagrammatic view of the bundled tube

Braced tube system
• Steel buildings-steel diagonals/trusses used
• Reinforced concrete buildings-diagonals are created
by filling the window openings by reinforced
concrete shear walls -diagonal bracing
• Braced tube structures are lateral load-resisting
systems- Located at the building perimeters made
the structural systems for tall buildings much more
efficient and economical.

Behavior under Gravity loading:-
• (a) - Intermediate columns will displace downward
by more than corresponding points on the
diagonal- controlled by the vertical displacement
of the less highly stressed corner columns.
• (b) - Downward forces on each diagonal are
carried at its ends by the corner columns -
compressive forces are increased at each
intersection with a diagonal = equalization of the
stresses in the intermediate and corner columns.

Behavior under lateral loading:-
• If the diagonals are initially disconnected from the
intermediate columns, the columns and diagonals of
the face will be in tension while the spandrels are in
compression .
• Because of the shear lag effect the intermediate
columns will now be less highly stressed than the
corner columns. the connection points on the
diagonals will be displaced upward by more than the
corresponding points on the unconnected
intermediate columns.

• If the diagonals and intermediate columns are
connected together, iterative vertical forces will be
mobilized
• These upward forces cause an increase in tension
in the intermediate columns

Types Material Efficient Height Advantages Disadvantages
Frame
d
Tube
Steel
80
Efficiently resists
lateral loads by locating
lateral systems at the
building perimeter.
Shear lag hinders
true tubular
behavior.
Narrow column
spacing
obstructs the
view.
Concrete
60
Brace
d
Tube
Steel
100 (With Interior
Columns) – 150
(Without Interior
Columns)
Efficiently resists lateral
shear by axial forces in
the diagonal members.
Wider column spacing
possible compared with
framed tubes. Reduced
shear lag.
Bracings obstruct
the view.
Concrete 100
Comparison of tube systems

Types Material Efficien
t
Height
Advantages Disadvantages
Bundl
ed
Tube
Steel 110
Reduced shear lag.
Interior planning
limitations due to
the bundled tube
configuration.
Concrete 110
Tube
in
Tube
Ext. Framed
Tube (Steel or
Concrete) + Int.
Core Tube (Steel
or Concrete)
80 Effectively resists
lateral loads by
producing interior
shear core - exterior
framed tube
interacting system.
Interior planning
limitations due to
shear core.

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Tube structures and its type with comparison .

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