Transcript Advantages of Rigid Frame Structure

HIGHRISE STRUCTURES
By
1.MOHAMED AYMAN
2.MOHAMED ELSAYED
3.MOHAMED ATEF
4.MOHAMED ALI
Under supervision of : prof. Ahmed Kamal
contents
•Introduction.
•LOADS ON THE HIGHRISE STRUCTURES
•Type of High-Rise Structure
•Conclusion.
High-rise structure
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high-rise is a tall building or structure.
• Buildings between 75 feet and
491 feet (23 m to 150 m) high are
considered high-rises.
Buildings taller than 492 feet (150
m) are classified as skyscrapers.
The materials used
• The materials used for the
structural system of high-rise
buildings are reinforced concrete
and steel.
 Most American style skyscrapers
have a steel frame, while
residential tower blocks are
usually constructed out of
concrete.
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Main features of High-rise structures
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• High-rise structures have
certain features. The structures
are high & lead to higher
vertical loads and higher lateral
loads (mainly due to wind
stress) in comparison with lower
buildings.
LOADS ON THE HIGHRISE STRUCTURES
 Vertical Loads:
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• Dead loads arise from the weigh to the
individual construction elements and the
finishing loads.
• Live loads are dependent on use
depending on the number of stories; live
loads can be reduced for load transfer
and the dimensioning of vertical loadbearing elements.
· However, the reduction of the total live
load on a construction element may not
exceed 40%.
Horizontal Loads:
 Calculation of lateral loads
should be carefully scrutinized.
 It generally arises from
unexpected deflections, wind
and earthquake loads
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Unexpected Deflections
It arises from imprecision in the
manufacture of construction
elements and larger
components.
 • Another cause is the uneven
settling of the foundation at an
in-homogeneous site.
 • Any deflection produces
additional lateral forces.
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Wind Loads
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• High-rise buildings are susceptible to
oscillation. It should not be viewed as
statically equivalent loads, but must be
investigated under the aspect of sway
behavior.
• Wind tunnel experiments are used to see
the influence of the building's shape on the
wind load.
• The ability of wind loads to bring a
building to sway must also be kept in
mind. This oscillation leads both to a
perceptible lateral acceleration for
occupants, and to a maximum lateral
deflection
Earthquake Loads
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Definition:
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• Seismology (from the Greek seism's=
earthquake and logos= word)
• scientific study of earthquakes
• propagation of elastic waves through the
Earth.
• studies of earthquake effects, such as
tsunamis
• diverse seismic sources such as volcanic,
tectonic, oceanic, atmospheric, and
artificial processes such as explosions
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Earthquake
• Produce different types of
seismic waves.
 • It travel through rock, and
provide an effective way to
image both sources and
structures deep within the
Earth.
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Seismic Waves
• There are three basic types of
seismic waves in solids:
 • Pressure waves
 • Shear waves
 • Pressure and/or Shear waves.
 • The two basic kinds of surface
waves (Raleigh and Love).
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Pressure waves
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• Travel at the greatest velocity
within solids and are therefore the
first waves to appear on a
seismogram.
• P-waves are fundamentally
pressure disturbances that
propagate through a material by
alternately compressing and
expanding (dilating) the medium,
where particle motion is parallel to
the direction of wave propagation.
Pressure waves
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• Travel at the greatest velocity
within solids and are therefore the
first waves to appear on a
seismogram.
• P-waves are fundamentally
pressure disturbances that
propagate through a material by
alternately compressing and
expanding (dilating) the medium,
where particle motion is parallel to
the direction of wave propagation.
Shear waves
• Transverse waves that travel
more slowly than P-waves and
thus appear later than P-waves
on a seismogram.
 • Particle motion is
perpendicular to the direction of
wave propagation. Shear waves
do not exist in fluids such as air
or water.
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Type of High-Rise Structure
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Braced Frame
Rigid Frame Structure.
In-filled Frame Structure
Flat Plate and Flat Slab Structure
Shear wall structure
Coupled wall structure
Wall-frame structure
Tube in tube or Hull core
structure
Bundled tube structure
Core and Outriggers system
Hybrid Structure
Braced Frame
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Braced frames are cantilevered vertical trusses
resisting laterals loads primarily through the axial
stiffness of the frame members.
• The effectiveness of the system, as characterized by
a high ratio of stiffness to material quantity, is
recognized for multi-storey building in the low to mid
height range.
• Generally regarded as an exclusively steel system
because the diagonal are inevitably subjected to
tension for or to the other directions of lateral loading.
• Able to produce a laterally very stiff structure for a
minimum of additional material, makes it an
economical structural form for any height of buildings,
up to the very tallest.
Advantages of Braced Frame
• Girders only participate
minimally in the lateral bracing
action-Floor framing design is
independent of its level in the
structure.
 • Can be repetitive up the
height of the building with
obvious economy in design and
fabrication.
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Disadvantages of Braced Frame
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• Obstruct the internal planning
and the locations of the windows
and doors; for this reason, braced
bent are usually incorporated
internally along wall and partition
lines, especially around elevator,
stair, and service shaft.-Diagonal
connections are expensive to
fabricate and erect
Rigid Frame Structure
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Consist of columns and girders joined by
moment resistant connections. Lateral
stiffness of a rigid frame bent depends on the
bending stiffness of the columns, girders, and
connection in the plane of the bents. Ideally
suited for reinforced concrete buildings
because of the inherent rigidity of reinforced
concrete joints. Also used for steel frame
buildings, but moment-resistant connections in
steel tend to be costly. While rigid frame of a
typical scale that serve alone to resist lateral
loading have an economic height limit of about
25 stories, smaller scale rigid frames in the for
of perimeter tube, or typically rigid frames in
combination with shear walls or braced bents,
can be economic up top much greater heights.
Advantages of Rigid Frame Structure
• May be place in or around the
core, on the exterior, or
throughout the interior of the
building with minimal constraint
on the planning module.
 • The frame may be
architecturally exposed to express
the grid like nature of the
structure.
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Advantages of Rigid Frame Structure
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The spacing of the columns in a
moment resisting frame can
match that required for gravity
framing.-Only suitable for
building up to 20 –30 stories
only; member proportions and
materials cost become
unreasonable for building higher
than that.
In-filled Frame Structure
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• Most usual form of construction for tall
buildings up to 30 stories in height Column
and girder framing of reinforced concrete, or
sometimes steel, is in-filled by panels of
brickwork, block work, or cast-in-place
concrete. Because of the in-filled serve also as
external walls or internal partitions, the
system is an economical way of stiffening and
strengthening the structure. The complex
interactive behavior of the infill in the frame,
and the rather random quality of masonry, has
made it difficult to predict with accuracy the
stiffness and strength of an in-filled frame.
Flat Plate and Flat Slab Structure
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• Is the simplest and most logical of all
structural forms in that it consists of uniforms
slabs, connected rigidly to supporting
columns.
• The system, which is essentially of
reinforced concrete, is very economical in
having a flat soft requiring the most
uncomplicated formwork and, because of the
soft can be used as the ceiling, in creating a
minimum possible floor depth.
• Lateral resistance depends on the flexural
stiffness of the components and their
connections, with the slab corresponding to
the girder of the rigid frame.
Flat Plate and Flat Slab Structure
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• Particularly appropriate for hotel
and apartment construction where
ceiling space is not required and
where the slab may serve directly as
the ceiling.
• Economic for spans up to about 25
ft (8m),above which drop panels can
be added to create a flat-slab
structure for span of up to 38 ft
(12m).
• Suitable for building up to 25
stories height.
Shear wall structure
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Concrete or masonry continuous vertical walls may
serve both architecturally partitions and structurally to
carry gravity and lateral loading. Very high in plane
stiffness and strength make them ideally suited for
bracing tall building Act as vertical cantilevers in the
form of separate planar walls, and as non-planar
assemblies of connected walls around elevator, stair
and service shaft. well suited to hotel and residential
buildings where the floor-by floor repetitive planning
allow the walls to be vertically continuous and where
they serve simultaneously as excellent acoustic and
fire insulators between rooms and apartments.
Minimum shrinkage restraint reinforcement where the
wall stresses are low, which can be for a substantial
portion of the wall.
Coupled wall structure
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• Consist of two or more shear walls in the same
plane, or almost the same plane, connected at the
floor levels by beam or stiff slabs.
• The effect of the shear-resistant connecting
members is to cause the sets of wall to behave in
their partly as a composite cantilever, bending
about the common centurial axis of the walls.
• Suited for residential construction where lateralload resistant cross walls, which separate the
apartments, consist of in-plane coupled pairs, or
trios, of shear walls between which there are
corridor or window openings. Besides using
concrete construction, it occasionally been
constructed of heavy steel plate, in the style of
massive vertical plate or box girders, as part of
steel frame structure.
Wall-frame structure
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The walls and frame interact horizontally, especially at
the top, to produce stiffer and stronger structure. The
interacting wall-frame combination is appropriate for
the building in the 40 –60 story range, well beyond
that of rigid frames or shear walls alone.
• Carefully tuned structure, the shear of the frame can
be made approximately uniform over the height,
allowing the floor framing to be repetitive. Although
the wall-frame structure is usually perceived as a
concrete structural form, with shear wall and concrete
frames, a steel counterpart using braced frames and
steel rigid frames offers similar benefits of horizontal
interaction.
• The braced frames behave with an overall flexural
tendency to interact with the shear mode of the rigid
frames.
The trussed tube
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The trussed tube system represents a classic solution for a
tube uniquely suited to the qualities and character of
structural steel.
• Interconnect all exterior columns to form a rigid box, which
can resist lateral shears by axial in its members rather than
through flexure.
• Introducing a minimum number of diagonals on each
façade and making the diagonal intersect at the same point
at the corner column.
• The system is tubular in that the fascia diagonals not only
form a truss in the plane, but also interact with the trusses
on the perpendicular faces to affect the tubular behavior. This
creates the x form between corner columns on each façade.
• Relatively broad column spacing can resulted large clear
spaces for windows, a particular characteristic of steel
buildings.
• The façade digitalization serves to equalize the gravity
loads of the exterior columns that give a significant impact
on the exterior architecture.
Tube in tube or Hull core structure
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This variation of the framed tube
consists of an outer frame tube, the
“Hull,” together with an internal elevator
and service core.
• The Hull and core act jointly in
resisting both gravity and lateral loading.
• The outer framed tube and the inner
core interact horizontally as the shear
and flexural components of a wall-frame
structure, with the benefit of increased
lateral stiffness.
• The structural tube usually adopts a
highly dominant role because of its much
greater structural depth.
Bundled tube structure
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The concept allows for wider column
spacing in the tubular walls than would
be possible with only the exterior frame
tube form.
• The spacing which make it possible to
place interior frame lines without
seriously compromising interior space
planning.
• The ability to modulate the cells
vertically can create a powerful
vocabulary for a variety of dynamic
shapes therefore offers great latitude in
architectural planning of a tall building.
Core and Outriggers system
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• Outrigger serve to reduce the
overturning moment in the core that
would otherwise act as a pure cantilever,
and to transfer the reduced moment to
columns outside the core by the way of
tension-compression coupled, which take
advantage of the increase moment arm
between these columns.
• It also serves to reduce the critical
connection where the mast is stepped to
the keel beam.
• In high-rise building this same benefit is
realized by a reduction of the base core
over-turning moments and the associated
reduction in the potential core uplift
forces.
Core and Outriggers system
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• In the foundations system, this core and
outrigger system can lead to the need for
the following:
• The addition of expensive and laborintensive rock anchors to an otherwise
“simple” foundation alternative such as
spread footing.
• Greatly enlarged mat dimensions and
depth solely to resist overturning forces.
• Time-consuming and costly rock sockets
for caisson systems along with the need to
develop reinforcement throughout the
complete caisson depth.
Core and Outriggers system
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• Expensive and intensive field work
connection at the interface between
core and the foundation. This
connection can become particularly
troublesome when one considers the
difference in construction tolerances
between foundations and core structure.
• The elimination from consideration of
foundation systems which might have
been nsiderably less expensive, such as
pile, solely for their inability to resist
significant uplift.
Advantages of Core and Outriggers system
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The outrigger systems may be formed in
any combination of steel, concrete, or
composite construction.
• Core overturning moments and their
associated induced deformation can be
reduced through the “reverse” moment
applied to the core at each outrigger
intersection. This moment is created by
the force couple at the exterior columns to
which the outrigger connect. It can
potentially increase the effective depth of
the structural system from the core only
to almost the complete building.
Advantages of Core and Outriggers system
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Significant reduction and possibly the complete elimination
of uplift and net tension forces throughout the column and
the foundation systems.
• The exterior column spacing is not driven by structural
considerations and can easily mesh with aesthetic and
functional considerations.
• Exterior framing can consist of “simple” beam and
column framing without the need for rigid-frame-type
connections, resulting in economies.
• For rectangular buildings, outriggers can engage the
middle columns on the long faces of the building under the
application of wind loads in the more critical direction. In
core-alone and tubular systems, these columns which carry
significant gravity load are either not incorporated or
underutilized. In some cases, outrigger systems can
efficiently incorporate almost every gravity column into
lateral load resisting system, leading to significant
economies.
Disadvantages of Core and Outriggers system
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The most significant drawback
with use of outrigger systems is
their potential interference with
occipital and rentable space.
Hybrid structure
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Combination of two or even more of basic structural
forms either by direct combination or by adopting
different forms in different parts of the structure. This
systems provide in-plane stiffness, its lack of Torsional
stiffness requires that additional measures be taken,
which resulted in one bay vertical exterior bracing and a
number of level of perimeter Vierendeel “bandages” –
perhaps one of the best examples of the art of structural
engineering.
Hybrid structures are likely to be the rule rather than the
exception for future very tall buildings, whether to create
acceptable dynamic characteristics or to accommodate
the complex shapes demanded by modern architecture.
High-strength concrete, consist of stiffness and damping
capabilities of large concrete elements are combined with
the lightness and constructability of steel frame exhibits
significantly lower creep and shrinkage and is therefore
more readily accommodated in a hybrid frame.