4204740.ppt

SEMINAR
PRESENTATION
ON
THE EFFICIENT USE OF OUTRIGGER AND BELT TRUSS
IN TALL BUILDINGS
Submitted to
MALAVIYA NATIONAL INSTITUTE OF TECHNOLOGY, JAIPUR
In partial fulfillment of the requirement for the award of Degree of
MASTER OF TECHNOLOGY
IN
STRUCTURAL ENGINEERING
Under the supervision of: Submitted By:
Dr. Ravindra Nagar Neeraj Agrawal
Professor (Structural Engg. Deptt.) M.Tech.(Structural Engineering)
MNIT Jaipur Student ID: 2010/PST/126
DEPARTMENT OF STRUCTURAL ENGINEERING,
MALAVIYA NATIONAL INSTITUTE OF TECHNOLOGY JAIPUR,
JAIPUR-302017

INTRODUCTION
Tall building with conventional
outriggers and belt truss
 The outrigger and belt
truss system is one of the
lateral loads resisting
system in which the
external columns are tied to
the central core wall with
very stiff outriggers and
belt truss at one or more
levels.
Taken from S. Fawzia and T. Fatima

 The belt truss tied the peripheral column of
building while the outriggers engage them with
main or central shear wall.
Strandard 3D view of Outrigger and belt truss
Taken from S. Fawzia and T. Fatima

 The aim of this method is to reduce obstructed
space compared to the conventional method.
 The floor space is usually free of columns and is
between the core and the external columns, thus
increasing the functional efficiency of the building.
 Exterior columns restrained the core wall from
free rotation through outrigger arms.

Outrigger and belt trusses, connect planar
vertical trusses and exterior frame columns.
 Outrigger system can lead to very efficient use
of structural materials by mobilizing the axial
strength and stiffness of exterior columns.

The great sailing ships of the past and present
use outriggers to help resist the wind forces in
their sails. Like the ship, the core in the tall
building can be related to the mast of the ship,
the outrigger acting like the spreaders and the
exterior columns like the stays or shroud of the
ship.
THE CONCEPT OF OUTRIGGER

THE USE OF OUTRIGGERS IN HIGH-RISE
BUILDINGS TO CONTROL THE FORCES
 The incorporation of an outrigger which connects
the two elements together provides a stiffer
component which act together to resist the
overturning forces.
 When an outrigger-braced building deflects under
wind or seismic load, the outrigger which connects to
the core wall and the exterior columns, makes the
whole system to act as a unit in resisting the lateral
load.

TYPES OF OUTRIGGER TRUSS
SYSTEM
On the basis of connectivity of core to exterior
columns, this system may be divided as in two
types :
1. CONVENTIONAL OUTRIGGER CONCEPT
2. VIRTUAL OUTRIGGER CONCEPT

CONVENTIONAL OUTRIGGER CONCEPT
In the conventional
outrigger concept, the
outrigger trusses or
girders are connected
directly to shear walls or
braced frames at the core
and to columns located
outboard of the core.
Typically (but not
necessarily), the columns
are at the outer edges of
the building.
Tall building with conventional outriggers
Taken from R. SHANKAR NAIR

VIRTUAL OUTRIGGER CONCEPT
 In the “virtual” outrigger concept, the same transfer
of overturning moment from the core to elements
outboard of the core is achieved, but without a
direct connection between the outrigger trusses and
the core.
 The basic idea behind the virtual outrigger concept
is to use floor diaphragms, which are typically very
stiff and strong in their own plane.

BELT TRUSSES AS VIRTUAL OUTRIGGERS
Tall building with belt trusses
as “virtual” outriggers
The use of belt trusses as
virtual outriggers avoids
many of the problems
associated with the use of
conventional outriggers.
The principle is the same as
when belt trusses are used
as virtual outriggers. Some
fraction of the moment in
the core is converted into a
horizontal couple in the
floors at the top and the
bottom of the basement. Taken from R. SHANKAR NAIR

ADVANTAGES OF USE OF BELT TRUSSES AS
VIRTUAL OUTRIGGERS
1. There are no truss diagonals extending from the
core to the exterior of the building.
2. The need to locate outrigger columns where they
can be conveniently engaged by trusses extending
from the core is eliminated.
3. The complicated truss-to-core connection is
eliminated.

4. Differential shortening or settlement between the
core and the outboard columns does not affect the
virtual outrigger system since the floor diaphragms,
though stiff in their own plane, are very flexible in
the vertical, out-of-plane direction.
Taken from R. SHANKAR NAIR

FACTORS AFFECTING THE EFFECTIVENESS OF
OUTRIGGER SYSTEM
1. The stiffness and location of the outrigger truss
system.
2. The stiffness and location of the Belt truss system.
3. Geometry of the tall building.
4. Stiffness of the central core.
5. Floor-to-floor height of the tall building.

Advantages of using Outrigger & Belt truss system
1. There are no trusses in the space between the
core and the building exterior.
2. There are fewer constraints on the location of
exterior columns. The need to locate large exterior
columns where they can be directly engaged by
outrigger trusses extending from the core is
eliminated.

3. All exterior columns (not just certain designated
outrigger columns) participate in resisting
overturning moment.
4. The difficult connection of the outrigger trusses to
the core is eliminated.
5. Core overturning moments can be reduced
through the reverse moment applied to the core at
each outrigger connection.

6. Exterior framing can consist of simple beam and
column framing without the need for rigid-frame-
type connection, thus reducing the overall cost.
7. Reduction or elimination of uplift and net tension
forces without the column and foundation system.

PLAZA RAKYAT TOWER
The 77-story Plaza Rakyat office
tower in Kuala Lumpur,
Malaysia, uses a concrete shear
core, a concrete perimeter
frame, exterior concrete belt
walls at two levels, and a
conventional outrigger system
at the roof as the building’s
lateral load-resisting system

JIN MAO TOWER
The 88-story Jin Mao Office, Hotel,
observation, retail tower is in Shanghai,
China. The tower is built around an
octagon-shaped concrete shear wall core
surrounded by 8 exterior composite super
columns and 8 exterior steel columns.
Three sets of 8 two-story high outrigger
trusses connect the columns to the core at
six of the floors to provide additional
support

TAIPEI 101
The 101-story TAIPEI-101 Office, Hotel,
observation, retail tower is in Shanghai,
China. The design achieves both strength
and flexibility for the tower through the
use of high-performance steel construction.
Thirty-six columns support Taipei 101,
including eight "mega-columns" packed
with 10,000 psi (69 MPa) concrete. Every
eight floors, outrigger trusses connect the
columns in the building's core to those on
the exterior.

CHIFLEY TOWER
The 42-story Chifley Tower Office,
financial institutions, law firms and
corporations tower is in Sydney, Australia.

CONCLUSTIONS ON TALL BUILDINGS USING
OUTRIGGER & BELT TRUSS
1. There are no trusses in the space between the
core and the building exterior.
2. There are fewer constraints on the location of
exterior columns. The need to locate large exterior
columns where they can be directly engaged by
outrigger trusses extending from the core is
eliminated.

3. All exterior columns (not just certain designated
outrigger columns) participate in resisting
overturning moment.
4. The difficult connection of the outrigger trusses
to the core is eliminated.
5. Complications caused by differential shortening
of the core and the outrigger columns are
avoided.

REFERENCES
3. Stafford Smith, B., Cruvellier, M., Nollet, M-J.,
and Mahyari, A. T., “Offset Outrigger Concept
for Tall Buildings,”
1. B.S. Taranath, Structural Analysis & Design
of Tall Buildings. New York, Mc Graw Hill,
1998.
2. R. S. Nair, Belt Trusses and Basements as
“Virtual” Outriggers for Tall Buildings.
Engineering Journal / Fourth Quarter/ 1998.

4. P.S. Kian and F.T.Siahaan, The use of outrigger
and belt truss system for high-rise concrete
buildings. Dimensi Teknit Sipil, Volume 3, No1,
Maret 2001, Page 36-41,ISSN1410-9530.
5. Smith, B. S., Coull, A. Tall Building
Structures: Analysis and Design. John Wiley
and Sons, Inc, New York.
6. S. Fawzia and T. Fatima, Deflection Control in
Composite Building by Using Belt Truss and
Outriggers Systems, Brisbane 4000, Australia.

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