Tos syllabus

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PRE FABRICATED
MODULAR STRUCTURES
GUIDED BY:
SOUMYA MISS
ASST PROFFESSOR,
UKFCET, KOLLAM
PRESENTED BY:
FAIZAL.A.M
7TH SEMESTER
CIVIL ENGINEERING
UKFCET, KOLLAM

Contents
Introduction
Features
Comparison
Design concept
Components
Types of precast system
Design consideration
Equipments
Assembling
scheduling
Advantages
Limitations
Conclusion
references
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Introduction
 The concept of precast structures also known as prefabricated/
modular structures.
 The structural components are standardized and produced in plants
in a location away from the building site.
 Then transported to the site for assembly.
 The components are manufactured by industrial methods based on
mass production in order to build a large number of buildings in a
short time at low cost.
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Features
The division and specialization of the human
workforce.
 The use of tools, machinery, and other equipment,
usually automated, in the production of standard,
interchangeable parts and products.
 Compared to site-cast concrete, precast concrete
erection is faster and less affected by adverse
weather conditions.
 Plant casting allows increased efficiency, high
quality control and greater control on finishes.
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Comparison
Site-cast
 no transportation
 the size limitation is
depending on the elevation
capacity only
 lower quality because
directly affected by weather
 proper, large free space
required
Precast at plant
transportation and elevation
capacity limits the size-
higher, industrialized quality
– less affected by weather
 no space requirement on the
site for fabrication
unlimited opportunities of
architectural appearance
option of standardized
components
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Design concept for precast concrete buildings
 The design concept
of the precast
buildings is based
on
 1.build ability.
 2.economy
3.standardization of
precast
components.
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Precast concrete structural elements
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Precast slabs
Precast Beam & Girders

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Precast Columns
Precast Walls

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Precast stairs
Precast concrete Stairs
Steel plates supported on 2 steel
beams

Design considerations
 final position and loads
 transportation requirements – self load and
position during transportation
 storing requirements – self load and position
during storing – (avoid or store in the same position
as it transported / built in)
 lifting loads – distribution of lifting points – optimal
way of lifting (selection of lifting and rigging tools)
 vulnerable points (e.g. edges) – reduction of risk
(e.g. rounded edges)
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Types of pre cast system
1. Large-panel systems
2. Frame systems
3. Slab-column systems with walls
4. Mixed systems
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box-like structure.
both vertical and horizontal
elements are load-bearing.
one-story high wall panels
(cross-wall system /
longitudinal wall system / two
way system).
one-way or two way slabs.
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1. Large-panel systems

2. Frame systems
Components are usually
linear elements.
The beams are seated on
corbels of the pillars usually
with hinged-joints (rigid
connection is also an
option).
 Joints are filled with
concrete at the site.
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3.Lift-slab systems
 - partially precast in plant (pillars)
/ partially precast on-site (slabs).
 - one or more storey high pillars
(max 5).
 - up to 30 storey high
constructions.
 - special designed joints and
temporary joints.
 -slabs are casted on the ground
(one on top of the other) – then
lifted with crane or special
elevators.
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Lift-slab procedure
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1. pillars and the first package (e.g. 5 pieces) of slabs prepared at
ground level
2. lifting boxes are mounted on the pillars + a single slab lifted to
the first floor level
3-8. boxes are sequentially raised to higher positions to enable the
slabs to be lifted to their required
final position - slabs are held in a relative (temporary) positions by
a pinning system

Planning traffic route
 How long transporter vehicle is
required?
 What is the required load capacity of
the transporter vehicle?
 What is the maximum vertical
extension of the shipment
 Routs on the site
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• Is route permission
required?

Equipments
cranes:
 mobile crane
 tower crane (above
3stories)
lifting tools:
 spreader beams
 wire rope slings
rigging tools:
 eye bolt
 shakles
 hooks
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Assembling….
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Column to column connection

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Precast concrete structure consisting of solid
wall panels and hollow core slabs.
Wall to slab connection

Advantages
Quick erection times
Possibility of conversion, disassembling
and moving to another site
Possibility of erection in areas where a traditional
construction practice is not possible or difficult
Low labor intensivity
Reduce wastage of materials
Easier management of construction sites
Better overall construction quality
Ideal fit for simple and complex structures
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Limitations
 size of the units.
 location of window openings has a limited variety.
 joint details are predefined.
 site access and storage capacity.
 require high quality control.
 enable interaction between design phase and production planning.
 difficult to handling & transporting.
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Scheduling
some approximate data for installation
 emplacement of hollow core floor slabs - 300 m2/day
 erection of pillars/columns - 8 pieces/day
 emplacement of beams - 15 pieces/day
 emplacement of double tee slabs - 25 pieces/day
 emplacement of walls - 15 pieces/day
 construction of stair and elevator shafts - 2 floors/day
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Examples….
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The hospital will feature multi-trade prefabricated racks in the corridors, an
approach that is still new in the U.S.

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Miami Valley Hospital Dayton,OH

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Conclusion
oThe use of prefabrication and preassembly is estimated
to have almost doubled in the last 15 years, increasing by
86%.
oThe use of precast concrete construction can significantly
reduce the amount of construction waste generated on
construction sites.
o Reduce adverse environmental impact on sites.
o Enhance quality control of concreting work.
o Reduce the amount of site labour.
o Increase worker safety .
o Other impediments to prefabrication and preassembly
are increased transportation difficulties, greater
inflexibility, and more advanced procurement
requirements.

LARGE SPAN
STRUCTURES
LARGE SPAN STRUCTURES

Large Span Systems
 Large span systems are structural systems whose dimensions exceed thelimits of standardbeams and slabsand thus require changes totheir
geometry, conﬁguration, or shape.
 In general, long span systems tend towards a handfull of basic types, relying on principles of bending, compression,
tensionto carry roof or ﬂoor loads overlarge distances.
 Large-span structures createunobstructed, column-free spaces greater than 30 m (100 feet)for avariety of functions.
The mostcommon types are :
or
simple beam
space frame
gable frame
foldedplates
cable stayed
truss
pre-stressed beam
suspension
pneumatic
arch castellated beam

 Large span structures are the structures that
provide large column free spaces.
 They are used in roofs for halls & other hall
type structures.
 They are composed of steel in the form of
truss system.
 They are quiet strong in nature
 They are unique because of their aesthetic
properties..
 For example they are used in airport,
railway station, stadium, assembly hall,
godown & temple etc.

 Materials suitable for various forms of long span and complex structure
span and complex structure
 1. All reinforced concrete including precast
 2. All metal (e.g. mild-steel, structural steel, stainless steel or alloyed
alumimum,
 3. All timber
 4. Laminated timber
 5. Metal/RC combined
 6. Plastic-coated Textile material
 7. Fiber reinforced plastic

 Common Structural Forms Common Structural Forms for Long Span
Building Structures for Long Span Building Structures
 1. Insitu RC, tensioned
 2. Precast concrete, tensioned
 3. Structural steel – erected on spot
 4. Structural steel – prefabricated and installed on spot
 5. Portal frame – insitu RC
 6. Portal frame – precast
 7. Portal frame – prefabricated steel

 Large span structures can be constructed by-
 Shell structures.
 Folded plate.
 Trusses
 Steel space frame.
 Coffered slab

SHELL STRUCTURES
 A SHELL STRUCTURE IS A THIN
CURVED MEMBRANE OR SLAB
USUALLY OF REINFORCED
CONCRETE THAT FUNCTIONS
BOTH AS STRUCTURE AND
COVERING.
 THE TERM “SHELL” IS USED TO
DESCRIBE THE STRUCTURES
WHICH POSSESS STRENGHT
AND RIGIDITY DUE TO ITS THIN,
NATURAL AND CURVED FORM
SUCH AS SHELL OF EGG, A NUT,
HUMAN SKULL, AND SHELL OF
TORTISE

 It transmits load more than 2
directions to support.
 It is highly efficient.
 Shaped, proportioned & supported
 It transmits load without bending or
twisting.
 Its thickness is small compared to its
other dimension.
 Deformation not large as compared to
its thickness.
 Consist of shearing stress which should
be normal to the middle surface and
should be negligible
 Application: Used in fuselages of aero
plane, boat hulls, roof structures.
• .. SHELLS OCCURING IN NATURE

 Depending upon the geometry of
middle surface the shells can be
classified as :
1.Domes
2.Shell Barrel Arch / Vault
3.Translation shells
4.Ruled Surfaces shell

DOMES
 Are hemispherical in shape.
 Used as roof structure.
 Constructed of stone , concrete &
brick.
 Supported on circular / regular
polygon shaped walls.
 Have certain height & diameter ratio.
 Have very small thickness.
 Can b constructed with or without
lanterns.
 Are of 2 types:
 i. Smooth shell domes & ii Ribbed
shell domes RIBBED SHELL DOMES
SMOOTH SHELL
DOMES

TYPES OF DOMES
SPHERICAL DOMES TRIANGULAR DOME
CYLINDERICAL DOME RECTANGULAR DOME

SHELL BARREL VAULT
 Is an Arched form.
 Used to provide a space with ceiling or roof.
 Elements of barrel shell:
*Curved membrane
*Tension zone
*Rise
*Span
*Width
*Edge beams
*End frame of diaphragm

TYPES OF SHELL VAULTS
MULTI BARREL VAULT CANTILEVER BARREL VAULT
SHORT SPAN BARREL VAULT NORTH LIGHT BARREL VAULT

TRANSLATION SHELL
 Is a type of shell structure.
 Dome set on four arches
 Different from spherical dome
 Easier to form than spherical dome
 Obtained by moving a vertical curve
parallel to itself along another vertical
curve usually in plane at right angles to
the plane of sliding curve.
 High tension forces in the corner.
 Special cases are:
1.Cylindrical shell &
2. Hyperbolic paraboloid

HYPERBOLIC PARABOLOID
 Is a special case of translation shell.
 Obtained by sliding a vertical parabola with
upward curvature on another parabola with
downward curvature in a plane at right angles to
the plane of first.
 Carries load on 2 directions.
 Diagonal element sags in tension
 Other element is an arch which is in compression.
 Consist of saddle surface.

STEEL SPACE FRAMES
 Are used in the form of grids of rectangular,
diagonal , triangular or hexagon pattern, arches
domes &other large column free areas.
 Highly efficient.
 Obtained by connecting the parallel trusses, not
by flexible elements but by transverse trusses as
rigid as the main truss.
 Deflection of the truss is transmitted to the
adjoining trusses & the entire roof works act
more or less monothically.
 Such special systems of hinged bar are called
SPACE FRAMES.
 Offers an economical solution to roofing of large
rectangular areas.
 Are stiffer than system of parallel trusses.
 Shallower in depth .

TYPES OF SPACE FRAMED SYSTEMS
 BRACED BARREL VAULT STRUCTURE
The braced double layer barrel vault is
composed of member elements arranged on
a cylindrical surface. The basic curve is a
circular segment; occasionally, a parabola,
ellipse or funicular line may also be used.
Its structural behavior depends mainly on the
type and location of supports, which can be
expressed as L/R, where L is the distance
between the supports in longitudinal direction
and R is the radius of curvature of the
transverse curve

 RIBBED DOME STRUCTURE
Ribbed dome is the earliest type of braced
dome that has been constructed . A ribbed
dome consists of a number of identical
meridional solid girders or trusses,
interconnected at the crown by a compression
ring. The ribs are also connected by concentric
rings to form grids in trapezium shape. The
ribbed dome is usually stiffened by a steel or
reinforced concrete tension ring at its base.

 GEODESIC DOMED STRUCTURE
The framework of these intersecting elements
forms a three-way grid comprising virtually
equilateral spherical triangles
 HIPPED END STRUCTURE
is a type of roof where all sides slope
downwards to the walls, usually with a
fairly gentle slope. Thus it is a house with
no gables or other vertical sides to the roof.
A square hip roof is shaped like a pyramid.
Hip roofs on houses could have two
triangular sides and two trapezoidal
ones. A hip roof on a rectangular plan has
four faces. They are almost always at the
same pitch or slope, which makes them
symmetrical about the centerlines

 POLYGONAL DOMED STRUCTURE
ADVANTAGES OF SPACE FRAMES
 One of the most important advantages of a
space structure is its lightweight. This is mainly
due to the fact that the material is distributed
spatially in such a way that the load transfer
mechanism is primarily axial — tension or
compression.
 Space frames can be built from simple
prefabricated units, which are often of
standard size and shape. Such units can be
easily transported and rapidly assembled
on site by semi-skilled labor. Consequently,
space frames can be built at a lower cost.
 A space frame is usually sufficiently stiff in spite
of its lightness. This is due to its three
dimensional character and to the full
participation of its constituent elements.
 Space frames possess a versatility
of shape and form and can utilize a
standard module to generate
various flat space grids, latticed
shell, or even free-form shapes.

What is the difference between truss and frame?
 1. Truss is essentially a frame and is fabricated using the structural steel.
2. Truss is a flexural member and is normally used for supporting a roof.
3.Truss is composed of many triangles connected together .
4. Frames, on the other hand have right angles between different members (
such as a door fame , window frame, portal frame )
 1- The joints in a truss are pinjointed whereas in case of frames rigid joints are
provided by bolting or welding. In a truss, the joints are pin type joints and the
members are free to rotate about the pin. As such, a truss cannot transfer
moments and members are subjected to only axial forces (tensile and
compression). On the other hand, members of frames are connected rigidly at
joints by means of welding and bolting. Therefore the joints of frames can
transfer moments in addition to the axial loads.
2- Truss memebers are designed for axial force(tensile or compression) only i.e.
there is no bending moment in trusses while on the other hand frames are
designed shear force and bending moment
 Trusses are 2 dimensional. Space frame 3-d
In a practical setting, you may see trusses with no flexibility in joints, but it is still
acceptable to analyze them as a perfect truss.

FOLDED PLATE STRUCTURES
 Consist of series of thin planer elements.
 Flat plates are connected to one another along their edges.
 Used in long span especially for roofs.
 Give mutual support to each other.
 Plates may be continuous over their supports longitudinally.
 Capable of transmitting both moment & shear or only shear.
 These plates carry the load from slab longitudinally to the
support.
 The support must be capable of resisting both horizontal &
vertical forces.
 Beam theory may be applied to design if the span is long.

TYPES OF FOLDED PLATE
PRISMATIC: if they consist of rectangular plates.
PYRAMIDAL: when consists of non-rectangular plates.
PRISMOIDAL: triangular or trapezoidal.
 FOLDED PLATE BEHAVIOR
Each plate is assumed to act as
a beam in its
plane ,this assumption is
justified when the ratio of
The span “length” of the plate
to its height
“width” is large enough . But
when this ratio is small,
the plate behaves as a deep
beam.

COFFERED SLAB STRUCTURES
 A coffer in architecture is a sunken panel in the shape of a
square, rectangle, or octagon in a ceiling, or vault.
 A series of these sunken panels were used as decoration
for a ceiling or a vault.
 Also known as caissons ('boxes"), or lacunaria ("spaces,
openings").
 The strength of the structure is in the framework of the
coffers.
 The stone coffers which is cut in soft tufa-like stone
reproduces a ceiling with beams and cross-beams lying on
them, with flat panels fillings the lacunae.
 Wooden coffers were first made by crossing the wooden
beams of a ceiling.
 Experimentation with the possible shapes of coffering,
which solve problems of mathematical tiling, or
tessellation, were a feature of Islamic as well as
Renaissance architecture.
 The more complicated problems of diminishing the scale
of the individual coffers were presented by the
requirements of curved surfaces of vaults and domes.
 Example of Roman coffering, employed to lighten the
weight of the dome, can be found in the ceiling of the
rotunda dome.

TRUSSES
 A truss is a structural frame based on the geometric rigidity of the triangle.
Linear members are subjected only to axial tension and compression. They
support load much like beams but for larger spans.
 To prevent secondary shear and bending stresses from developing, the
centroidalaxes of the truss members and the load at a joint should pass
through a common point

Different types of Wooden and Steel Roof Trusses:
 King Post Truss
 Queen Post Truss
 Howe Truss
 Pratt Truss
 Fan Truss
 North Light Roof Truss/ SAWTOOTH TRUSS
 Quadrangular Roof Truss
 Tubular Steel Roof Truss
 Tubular Monitor Steel Roof Truss
King Post Truss
•King Post Truss is a wooden truss.
•It can also be built of combination of wood
and steel.
•It can be used for spans upto 8m.

 Queen Post Truss
•Queen Post Truss is also a wooden
truss.
•It can be used for spans upto 10m.
 Howe Truss
•It is made of combination of wood and
steel.
•The vertical members or tension members
are made of steel.
•It can be used for spans from 6-30m.
 Pratt Truss
•Pratt Truss is made of steel.
•These are less economical than the Fink
Trusses.
•Vertical members are tension and diagonal
members are compression.
•Fink Trusses are very economical form of roof
trusses.

Fan Truss
•It is made of steel.
•Fan trusses are form of Fink roof truss.
•In Fan Trusses, top chords are divided into
small lengths in order to provide supports for
purlins which would not come at joints in Fink
trusses.
 North Light Roof Truss
•When the floor span exceeds 15m, it is generally more
economical to change from a simple truss arrangement to one
employing wide span lattice girders which support trusses at right
angles.
•In order to light up the space satisfactorily, roof lighting has to
replace or supplement, side lighting provision must also be made
for ventilation form the roof.
•One of the oldest and economical methods of covering large areas
is the North Light and Lattice girder.
•This roof consists of a series of trusses fixed to girders. The short
vertical side of the truss is glazed so that when the roof is used in
the Northern Hemisphere, the glazed portion faces North for the
best light.
•Used for industrial buildings, drawing rooms etc.

 Quadrangular roof Trusses
• These trusses are used for large spans such as
railway sheds and Auditoriums.
LARGE SPAN TRUSSES
TUBULAR STEEL ROOF TRSSES are
used for large span constructions such as
factories, industry worksheds, shopping
malls, huge exhibition centres, multiplexes
etc. They are generally used for spans as
large as 25-30m.

 Advantages of Tubular Steel Roof Trusses
• Structures designed for material handling equipments (e.g., a bridge and
a tower crane) where weight savings may be very substantial economic
consideration.
• 30% to 40% less surface area than that of an equivalent rolled steel
shape. Therefore, the cost of maintenance, cost of painting or protective
coatings reduce considerably.
• The moisture and dirt do not collect on the smooth external surface of
the tubes. Therefore, the possibility of corrosion also reduces.
• The ends of tubes are sealed. As a result of this, the interior surface is
not subjected to corrosion. The interior surface do not need any
protective treatment.
• They have more torsional resistance than other section of the equal
weight.
• They have a higher frequency vibrations under dynamic loading than the
other sections including the solid round one.

•The Vierendeel truss/girder is characterized by having only vertical members between the top and bottom chords and is a
statically indeterminate structure. Hence, bending, shear and axial capacity of these members contribute to the resistance
to external loads.
•The use of this girder enables the footbridge to span larger distances and present an attractive outlook.
•However, it suffers from the drawback that the distribution of stresses is more complicated than normal truss structures.
VIERENDEEL TRUSS
•Elements in Vierendeel trusses are subjected to bending, axial force and shear , unlike conventional trusses with
diagonal web members where the members are primarily designed for axial loads
DISADVANTAGES
•Vierendeel trusses are usually more expensive than
conventional trusses.
•Their use limited to instances where diagonal web
members are either obtrusive or undesirable
•but the resulting joints are often very heavy in
appearance.
LOAD DISTRIBUTION
Vierendeel trusses are moment resisting. Vertical members
near the supports are subject to the highest moments and
therefore require larger sections to be used than those at
mid-span. Considerable bending moments must therefore
be transferred between the verticals and the chords, which
can result in expensive stiffened details.
ADVANTAGES
•The joints may be heavy, but the absence of diagonals makes
this form suitable for storey-height construction.
•Using standard computer programs, the analysis is not
difficult, However the system does allow full storey-height
construction without obstruction to openings.
Vierendeel bridge at Grammene, Belgium

The term ‘tensile structures’ covers a broad category
of structures:
•Fabric membranes
•Pre-stressed cable nets
•Cable beams in form of trusses and girders
•Although compression, bending and shear maybe
present in some of these structures, tension stress is
more prominent.
•Compared to bending and compression , tensile
elements are more efficient as they use the material
to its full capacity.
•Bending elements use only half the material
effectively, since bending stress varies from
compression to tension with zero stress at neutral
axis.
•Compression elements are subjected to bucking of
reduced capacity as slenderness increases.
•However, the efficiency of tensile structures
depends greatly on the type of support.
Tensile structures are characterized by the
prevalence of tension force in their structural
systems and by limitation of compression
Forces to a few support members. Thus
These lightweight structures do not require
The considerable amount of construction
Material to absorb the Buckling and bending
Moments in compression members.
Tension
Compression

Elements of a membrane structure:
•Highly flexible fabric held under tension in order to generate stiffness in surface
•One-dimensional flexible elements i.e. ties or cables to creates ridges, valleys and edge boundaries
•Rigid support members sustaining compression/bending
Note: Cable structures are constructed using a combination of the first two elements.
Cable structures can be tensioned by applying direct axial forces to the cables or by loading free
suspended cables with heavy cladding/decking.

Three main categories:
•Boundary tensioned membranes
•Pneumatic structures
•Pre-stressed cable nets and beams
Boundary Tensioned Membranes
•Lightweight (typically 0.7–1.4 kg/m2 ), highly flexible
membranes with a level of pre-tension which
generates stiffness in the surface.
•The overall equilibrium of the structure is provided by
rigid edges and supporting members generally
subjected to compression and/or bending.
•Under imposed load due to snow or wind, the fabric
surface undergoes large displacements and a
consequent increase in the material stress, which can
increase up to ten fold. For this reason a safety factor
higher than four is highly recommended.
•Membrane structures are basically realised with
coated fabrics, with growing interest towards open
mesh coated fabrics and foils.
•Coating layer can be of either PVC, PTFE
(polytetrafluroethlyene) or PVDF (polyvinylidine
difluride)

Pneumatic Structures
•The term pneumatic structures includes all
the lightweight structures in which the load
bearing capacity is achieved by means of air
under pressure.
•They are mainly subdivided into two
categories: the buildings characterised by a
single layer, stabilised by a slight difference in
pressure between the inside and the outside
of the structures, and the building envelopes
stabilised by air under pressure enclosed
between two or more membrane layers.
•Air-supported structures provide a cost effective alternative for seasonal wide span coverings, nevertheless,
the reduced resistance under bad weather conditions combined with high costs due to great pressure losses,
reduced insulation, maintenance and the seasonal mounting and dismounting costs can progressively reduce
the initial convenience over the entire life span

Pre-stressed Cable Nets, Beams and Domes
•Cable structures are load bearing structures composed of linear flexible elements under tension, with
the only exception being rigid members or supports such as rigid ring beams or masts.
•They can be subdivided in cable nets, which describe three-dimensional surfaces, cable domes and
their two-dimensional version represented by cable trusses.
•Cable nets share the basic physical principles which regulate their equilibrium and shape with the
boundary tensioned membranes described above.
•Cable domes are based on a slightly different structural scheme which is generally circular in plan and
based on radial trusses made of cables with the only exception of vertical compression struts.
•Cable trusses mostly present a planar structure, with a top cable and a bottom cable with a
considerable cross-sectional area due to their load bearing function.
•The load bearing capacity of pre-stressed cable nets, domes and beams depends on the geometry
chosen, the level of pre-stress and the allowable deformation and fatigue strength of each member,
the higher the pre-tension the lower the deflection under external loads, but with a consequent
increase in costs and material stress.

Cables can be of mild steel, high
strength steel , stainless steel or
polyester or aramid fibres.
Structural cables are made of a series
of small strands twisted or bound
together to form a much larger cable.
The tensioned members are termed as
cables are group of wires, strands or ropes.
A wire is a continuous length of steel that
has a circular cross section. Cables do not
loose strength in
case of failure of one wire. The wires in the
strand are zinc coated and stranded into
helix whichforms a regular cross section.
Cables

Cable Stayed Structures
•Usually used in bridges.
•Adaptation of suspension bridge principle.
•The deck structure is supported by tension stays sloping from one or more towers.
•There may be either a single plane of stays down the centre of the bridge, or two planes;
one on each side of the bridge.
•The towers act in compression and can have a variety of forms (A-frame, H-frame or
columns). The deck girders sustain compression forces as well as bending forces.
•Economic spans range from 200m to over 850m, and as such cable-stayed bridges fill the
gap between large arches / trusses and small suspension bridges.
•Span/depth ratio is an important design factor-A shallow depth results in great tension and
compression in stays and beams respectively, a steep slope has opposite effect.

Cable Suspended Structures
•Used for long-span roofs.
•Suspended cables effectively resist gravity loads in tension burt are unstable under wind
uplift and uneven loads.
•Suspended Structures are those with horizontal planes i.e. floors are supported by cables
(hangers) hung from the parabolic sag of large, high-strength steel cables. The strength of a
suspended structure is derived from the parabolic form of the sagging high strength cable.
To make this structure more efficient, the parabolic form is so designed that its shape
closely follows the exact form of the moment diagrams.
•The large curving cable may consist of many smaller cables which are tightly spun together.
As the cables are being spun together, they are also stretched over the span and attached
to the supports.

•Stadiums
•Stages
•Covered malls
•Walkways
•Play areas
•Entrances
•Atriums
•Sports arenas
•Airports
•As fabric cladding panels

•Unique building medium.
•Lightweight and flexible, fabric interacts with and expresses natural forces.
•Fabric structures have higher strength/weight ratio than concrete or steel. Most fabrics can be A fabric
structure can be designed for almost any condition, heavier fabrics and more 3 dimensional frecycled.
•forms will cope with extreme wind and snow loads.
•Translucency – In daylight, fabric membrane translucency offers soft diffused naturally lit spaces reducing
the interior lighting costs while at night, artificial lighting creates an ambient exterior luminescence.
•Low Maintenance – Tensile membrane systems are somewhat unique in that they require minimal
maintenance when compared to an equivalent-sized conventional building.
•Cost Benefits – Most tensile membrane structures have high sun reflectivity and low absorption of
sunlight, thus resulting in less energy used within a building and ultimately reducing electrical energy
costs.
•Fabric structures being mainly fabric and cables have little or no rigidity and therefore must rely
on their form and internal pre-stress to perform the this function.
•As a rule of thumb spans greater than 15 metres should be avoided however, much greater spans
can be achieved by reinforcing the fabric with webbing or cables.
•Loss of tension is dangerous for the stability of the structure and if not regularly maintained will
lead to failure of the structure.

A space frame is a truss-like, lightweight rigid structure constructed
from interlocking struts in a geometric pattern.
• A three-dimensional structures.
• The assembled linear elements are arranged to transfer the load.
• Take a form of a flat surface or curve surface.
• Designed with no intermediate columns to create large open
area.
• Space frames usually utilize a multidirectional span, and are often
used to accomplish long spans with few supports.
• They derive their strength from the inherent rigidity of the
triangular frame; flexing loads (bending moments) are
transmitted as tension and compression loads along the length of
each strut.
SHASHI | SHRISHTI
• Space frames are an increasingly common architectural technique
especially for large roof spans in modernist commercial and
industrial buildings

SHASHI | SHRISHTI
TYPES OF SPACE FRAMES
According to curvature
1- Flat covers
These structures are composed of planar substructures. The
plane are channeled through the horizontal bars and the shear
forces are supported by the diagonals.
2- Barrel vaults
This type of vault has a cross section of a simple arch. Usually
this type of space frame does not need to use tetrahedral
modules or pyramids as a part of its backing.
3- Spherical domes
These domes usually require the use of tetrahedral modules or
pyramids and additional support from a skin.
According to the number of grid layers
1- Single-Layer
All elements are located on the surface to be approximated.
2- Double-Layer
The elements are organized in two parallel layers with each
other at a certain distance apart. The diagonal bars
connecting
the nodes of both layers in different directions in space.
3- Triple-Layer
Elements are placed in three parallel layers, linked by the
diagonals. They are almost always flat. This solution is to
decrease the diagonal members length.

SHASHI | SHRISHTI
TYPES OF SPACE FRAME
1) Two and three-way grids
 Characterized as two way or three way
2) Single, Double and Triple Layered
 Single layer frame has to be singly or doubly
curved.
 Commonly used space frames are double
layered and flat.
 Triple layered is practically used for a large
span building.
i. Skeleton (braced) frame work e.g. domes, barrel vaults, double and multiplier grids,
braced plates. They are more popular. They are innumerable combinations and
variation possible and follow regular geometric forms.
ii. Stressed skin systems e.g. Stressed skin folded plates, stressed skin domes and
barrel vaults, pneumatic structures.
iii. Suspended (cable or membrane) structures e.g. Cable roofs

SHASHI | SHRISHTI
COMPONENTS OF SPACE FRAME
 Consists of axial members : which are tubes and connectors
 TUBES
1) CIRCULAR HOLLOW SECTIONS
2) RECTANGULAR HOLLOW SECTIONS
 CONNECTORS
1) Tuball Node Connector
 A hollow sphere made of spheroidal graphite
 The end of the circular hollow section member to be connected is
fitted at its ends by welding.
 Connection from inside the cup is using bolt and nut.
2) Nodus Connector
• It can accept both rectangular and circular hollow sections and that the
cladding can be fixed directly to the chords.
• Chord connectors have to be welded to the ends of the hollow
members on site.

SHASHI | SHRISHTI
3) Triodetic Connector
• It consists of a hub, usually an aluminium extrusion, that has slots or
key ways, which the ends of members are pressed or coined to match
the slots.
4) Hemispherical Dome Connector
• Usually use for double layer domes.
• Has a span more than 40m.
• More economical for long span.
• The jointing is connect by slitting the end of the tube or rod with the
joint fin.
• There are 2 types of joint, pentagonal joint and hexagonal joint.
Load Distribution
Some space frame applications include:
• Hotel/Hospital/commercial building entrances
• Commercial building lobbies/atriums
• Parking canopies
Tension

SHASHI | SHRISHTI
METHOD OF SUPPORT
1. Support along perimeters—This is the most commonly
used support location. The supports of double layer grids
may directly rest on the columns or on ring beams
connecting the columns or exterior walls. Care should be
taken that the module size of grids matches the column
spacing.
2. Multi-column supports—For single-span buildings, such
as a sports hall, double layer grids can be supported on
four intermediate columns . Figure 13.5a
For buildings such as workshops, usually multi-span
columns in the form of grids . Figure 13.5b
Sometimes the column grids are used in combination with
supports along perimeters . Figure 13.5c
Overhangs should be employed where possible in order to
provide some amount of stress reversal to reduce the
interior chord forces and deflections. Figure 13.6
3. Support along perimeters on three sides and free
on the other side—For buildings of a rectangular shape, it
is necessary to have one side open, such as in the case of
an airplane hanger or for future extension.

SHASHI | SHRISHTI
Advantages of space frame systems over conventional systems:
• Random column placement
• Column-free spaces
• Minimal perimeter support
• Controlled load distribution
• Design freedom
• Supports all types of roofing
• Light
• Elegant & Economical
• Carry load by 3D action.
• High Inherent Stiffness
• Easy to construct
• Save Construction Time & Cost
• Services (such as lighting and air conditioning) can be integrated with space
frames
• Offer the architect unrestricted freedom in locating supports and planning the
subdivision of the covered space.

SHASHI | SHRISHTI
Advantages of Space Frames
1. Lightweight
This is mainly due to the fact that material is
distributed spatially in such a way that the load
transfer mechanism is primarily axial; tension
or compression. Consequently, all material in
any given element is utilized to its full extent.
Furthermore, most space frames are now
constructed with aluminum, which decreases
considerably their self-weight.
2. Mass Productivity
Space frames can be built from simple
prefabricated units, which are often of standard
size and shape. Such units can be easily
transported and rapidly assembled on site by
semi-skilled labor. Consequently, space frames
can be built at a lower cost.
3. Stiffness
A space frame is usually sufficiently stiff in
spite of its lightness. This is due to its
three-dimensional character and to the full
participation of its constituent elements.
4. Versatility
Space frames possess a versatility of shape
and form and can utilize a standard module to
generate various flat space grids, latticed shell,
or even free-form shapes. Architects
appreciate the visual beauty and the
impressive simplicity of lines in space frames.

SHASHI | SHRISHTI
Disadvantages of Space Frames
1. Cost
The main criticism of space grids is their cost, which can
be high when compared with alternative structural
systems. This is particularly true when space grids are
used for short spans.
2. Visually busy structures
Visually, space grid structures are very 'busy'. They are
rarely seen in plan or in true elevation and at some viewing
angles the lightweight structure can appear to be very
dense. Grid size and depth as well as the grid configuration
can have considerable influence on the perceived density of
the structure.
3. Longer erection times
The number and complexity of joints can lead to longer
erection times on site. This is obviously very dependent on
the system being used and the grid module chosen.
4. Large surface area
When space grids are used to support floors some form
of fire protection may be required. This is difficult to
achieve economically due to the high number and relatively
large surface area of the space grid elements

SHASHI | SHRISHTI
SPACE FRAME METHODS OF ERECTION
• The method chosen for erection of a space frame depends on its behavior of load
transmission and constructional details, so that it will meet the overall requirements of quality,
safety, speed of construction, and economy.
• The scale of the structure being built, the method of jointing the individual elements, and the strength and rigidity of
the space frame until its form is closed must all be considered.
1- SCAFFOLD METHOD
Individual Elements are Assembled in Place at
Actual Elevations, members and joints or
prefabricated subassembly elements are
assembled directly on their final position. Full
scaffoldings are usually required for this type of
erection. Sometimes only partial scaffoldings
are used if cantilever erection of space frame
can be executed. The elements are fabricated at
the shop and transported to the construction
site, and no heavy lifting equipment is required.
2. BLOCK ASSEMBLY METHOD
The space frame is divided on its plan into individual strips or blocks. These
units are fabricated on the ground level, then hoisted up into its final
position and assembled on the temporary supports. With more work
being done on the ground, the amount of assembling work at high
elevation is reduced. This method is suitable for those double-layer grids
where
the stiffness and load-resisting behavior will not change considerably after
dividing into strips
or blocks, such as two-way orthogonal latticed grids, orthogonal square
pyramid space grids, and the those with openings. The size of each unit
will depend on the hoisting capacity available.

SHASHI | SHRISHTI
EXAMPLES OF POPULAR BUILDINGS WITH SPACEFRAMES
INDIAN HABITAT CENTRE , LODHI ROAD JEEVAN BHARTI BUILDING, CP
HALL OF NATIONS, PRAGTI MAIDAN STANSED AIRPORT, LONDON
RAILWAY STATIONS SUPPORTED BY BARREL VAULT STRUCTURE LOUVRE PYRAMID, LOUVRL PALACE, PARIS

SHASHI | SHRISHTI
JOINTING SYSTEMS AND TERMINOLOGY
JOINTING SYSTEMS
• The jointing system is an extremely important part of a space frame design. The joints for the space frame are more important than the
ordinary framing systems because more members are connected to a single joint
• Also, the members are located in a three dimensional space, and hence the force transfer mechanism is more complex
• The type of jointing depends primarily on the connecting technique, whether it is bolting, welding, or applying special mechanical
connectors. It is also affected by the shape of the members.
• This usually involves a different connecting technique depending on whether the members are circular or square hollow or rolled steel
sections.
• Requirements considered for designing the jointing systems :-The joints must be strong and stiff, simple structurally and mechanically, and
easy to fabricate without recourse to more advanced technology and joints of space frames must be designed to allow for easy and
effective maintenance
• All connectors can be divided into two main categories: the purpose-made joint and the proprietary joint used in the industrialized system
of construction
• Purpose-made joints-usually used for long span structures where the application of standard proprietary joints is limited.
Example -cruciform gusset plate for connecting rolled steel sections.
• All the connection techniques can be divided into three main groups: (1) with a node
(2) without a node, and (3) with prefabricated units.
TERMINOLOGIES
• Aspect ratio: Ratio of longer span to shorter span of a rectangular space frame.
• Braced (barrel) vault: A space frame composed of member elements arranged on a
cylindrical surface.
• Braced dome: A space frame composed of member elements arranged on a spherical surface.
• Depth: Distance between the top and bottom layer of a double layer space frame.
• Double layer grids: A space frame consisting of two planar networks of members forming the top and bottom layers parallel to each other
and interconnected by vertical and inclined members.
• Geodesic dome: A braced dome in which the elements forming the network are lying on the great circle of a sphere.
• Lamella: A unit used to form diamond shaped grids, the size being twice the length of the side of the diamond.
• Latticed grids: Double layer grids consisting of intersecting vertical latticed trusses to form regular grids.
• Latticed shell: A space frame consisting of curved networks of members built either in single or double layers.
• Latticed structure: Astructuralsystemintheformofanetworkofelementswhoseload-carrying mechanism is three-dimensional in nature.
• Local buckling: A snap-through buckling that takes place at one point.
• Module: Distance between two joints in the layer of grid.
• Space frame: A structural system in the form of a flat or curved surface assembled of linear elements so arranged that forces are transferred
in a three-dimensional manner.
• Space grids: Double layer grids consisting of a combination of square or triangular pyramids to form offset or differential grids.
• Space truss: A three-dimensional structure assembled of linear elements and assumed as hinged joints in structural analysis.

Arunima G
Prabhnoor S
Raunak R
Saurabh K
Sudhanshu M
Tanvi G
Steel Trusses

Steel Trusses
Introduction
• Steel trusses were taken up as against wooden trusses because the scarcity of quality timber was increasing
in manyareas.
• Steel is alsoa superior buildingconstruction material when compared to wood. Unlike timber, it is a
homogenous and isotropic material, i.e. it has same characteristics in all directions.
• Another major advantage steel provides in roof trusses is that it is much lighter and often more economical in
large roof systems.
Tension

Steel Trusses
Roof truss design
The following are the conditions that influence the design of aroof truss:
1. Loads:
Roof trusses are especially adapted to such buildings where they support the roof and still afford a clear space without the use of
intermediate columns. They support loads of various kinds, such as the dead load, due to the weight of material used in constructing
and covering the roof, the wind load, the snow load, and frequently the weight of plastered ceilings, as well as loads from
attic floors and from suspended platforms and galleries. In laying out the stress diagrams, all these loads are considered, and
both members and details are then proportioned to withstand the various stresses produced. Purlins, that rest on and connect the
trusses at their panel points, or points at which the main rafter and the web members intersect. These purlins support the rafters of
the roof, on which the wood sheathing and roofing material are placed. In iron and steel construction I beams and Z bars are
generally employed. Great care should be taken to avoid, as far as possible, the accidental stresses to which trusses are so often
subjected duringerection, and which can scarcely be calculated.
2. Slope of Roof:
The character of the roofingmaterial must be consideredin determining the direction of the upper chord.
For instance, when shingles are used, the pitch should not be less than 1 of rise to 2 of run, while with slates if the pitch is less
than 1 to 3, the wind is liable to blow the rain under the slate, thereby causing leaks. A slope of 1 to 2, however, is preferable for slate,
although, when occasion requires, the minimum pitch of 1 to 3 may be employed. Corrugated iron is liable to leak if laid with a
pitch of less than 1 to 3, while in a gravel and tar roof, if the slope is greater than 1 to 4, the heated tar is apt to run down
and collect at the lower portion of the roof, leaving the upper part exposed and unprotected, and rain falling on such a roof flows
off so quickly that the pebbles are washed out of the roofing.
Flat clay tile set in asphalt may be used on flat roofs, but clay and metal tile simulating corrugated or Spanish tile are usually
laid with a pitchsomewhatgreater than 1 to 2.

Steel Trusses
Roof truss design
3. Distance between Trusses:
The fact that the economyof the design is so largely dependent on the spacing of the trusses, makes it necessary that an
effort be made to ascertain the distance that may most economically exist between them.This is especiallythe case when the
building over which they are to be placed is of sucha character that the spacing of the trussesgoverns, or, at least, affects the
exteriordesign. Often, too, the engineer is restricted by the fact that the size of the lot must be considered when determining the size
of the building, and hence, the distancebetween the trusses is influencedto a certain degree, particularly when architectural effect is
desired.
4. Material used:
The general design of a truss is influenced by the material employed in its construction, and the choice of material is influenced by
its costand availability, as well as by the span of the truss and the loadsthat come on it. When the span exceeds 80 feet, and the loads
are comparativelyheavy, steel is usuallythe best material to use; but if steel is unavailable, timbermay be used for trusses having
spans as great as 150 feet. When timber trusseshave as great a spanas this, they are usually arched, and built in pairs. While steelmay
be used for the construction of trusses of all spans,great and small, the designer is frequentlycompelled to use timber because the
costof the work is limited.
5. After the general dimensions of the roof truss have been determined, if economy is to be considered, the cost mustbe
investigated. Shouldthe conditions admit a choiceof several designs, it is often desirableto estimate the cost of each, and
adopt the one whose construction costs the least. In designing trussesit is generally cheaper to use stock sizes of timber or steel
shapes, for by so doing,even though the membersare of a largersize than actually required, the work is usually facilitated to such
an extent that the timerequired in its performance is materially reduced, whichis frequently a factorof the utmostimportance.

Steel Trusses
System options
Steelsectionsare available in many different extrusiontypes and systems, the following may be used for steel roof trusses:
Angle and flat bar truss:
• Small angle bars may be welded directlyonto each other forming very
light trusses up to about 12 m span.
• The length of the compression members mustbe reduced as muchas
possible to avoid buckling.This results in trusses with a large numberof
diagonalsand connections.
• Examples: Fink or Polonceau Truss.
Steel tube truss:
• Steel tubes are readily available throughout the worldand at reasonable
prices,since they are also used for steel pipes and pipingsystems.
• The jointing of the round surfacesis difficult; buttand fillet welding of
properly cut and shaped tubesis possiblebut slow and expensive.
• When usingtubes, the number of connections per truss should be
reduced as much as possible.

Steel Trusses
System options
Rolled sections truss:
• Rolled sections other than angle bars used in truss designs are the
channeland universal beams.
• Half-section universal beams are particularly useful in truss design but are
not readilyavailable.
• Used in trusses of spans larger than 12 m.
Rectangularhollow section truss:
•
•
RHS providea particularly neat appearance of steel trusses.
Welded connections are common thanksto the regularshapes of the
RHS.
• RHS are particularly expensive and are not readily available in many
countries.

PINNED/BOLTED CONNECTIONS
TYPICALLY, THE JOINT CONNECTIONS ARE FORMED BY BOLTING OR WELDING THE END MEMBERS
TOGETHER TO A COMMON PLATE, CALLED A GUSSET PLATE.
JOINING DETAILS
Generally in steelwork construction, bolted site splices are preferred to welded splices for economy and
speed of erection.

•CHORDS The outer members of a truss that defi ne the envelope or
shape.
• TOP CHORD An inclined or horizontal member that establishes the
upper edge of a truss. This member is subjected to compressive and
bending stresses.
•BOTTOM CHORD The horizontal (and inclined, ie. scissor trusses)
member defining the lower edge of a truss, carrying ceiling loads
where applicable. This member is subject to tensile and bending
stresses. (On a simply supported, non-cantilevered truss).
•CLEAR SPAN The horizontal distance between inside faces or
supports.
•HEEL The joint in a pitched truss where top and bottom chords meet.
•HEEL HEIGHT - The "thickness" of a truss at the end of the Bottom
Chord. Measured from the bottom of the Bottom Chord (or top of top
plate) to the top of the Top Chord (underside of sheathing) at the end
of the truss.
•JOINT The point of intersection of a chord with the web or webs, or
an attachment of pieces of lumber (eg. splice)
•LATERAL BRACE A permanent member connected to a web or chord
member at right angle to the truss to restrain the member against a
buckling failure, or the truss against overturning.
•OVERHANG The extension of the top chord beyond the heel joint.
•OVERALL HEIGHT - - A vertical measurement taken at the midpoint
of a truss from the bottom of the Bottom Chord to the peak.
•PANEL The chord segment between two adjacent joints.
•PANEL POINT The point of intersection of a chord with the web or
webs.
•PANEL LENGTH - The horizontal distance between the centerlines of
two consecutive panel points along the top or bottom chord.
• PEAK Highest point on a truss where the sloped top chords meet.
•SLOPE (PITCH) The units of horizontal run, in one unit of vertical rise
for inclined members. (Usually expressed as 3:12, 5:12, etc.)
•SPLICE POINT The location where the chord member is spliced to
form one continuous member. It may occur at a panel point but is
more often placed at 1/4 panel length away from the joint.
•WEBS Members that join the top and bottom chords to form the
triangular patterns that give truss action. The members are subject
only to axial compression or tension forces (no bending)
•WEDGE - THE TRIANGULAR PIECE OF LUMBER INSERTED BETWEEN
THE TOP AND BOTTOM CHORDS, USUALLY TO ALLOW THE TRUSS TO
CANTILEVER.

Metal Roof Truss – Advantages and Disadvantages of Metal Roof Truss Structures.
Metal roof trusses, just like wood trusses, have their advantages and disadvantages. Some builders prefer to the metal roof
truss because the building of a structure is all about precision and metal has a more precise measurement than wood.
Safety is also an issue when deciding to use a metal roof truss or a wood truss system, building codes and other procedures
may require certain trusses.
Advantages of Metal Roof Truss Structures
•Even though they are considered to be more expensive, metal roof trusses can span further than wood.
•Metal roof trusses can be manufactured to exact standards.
•They are much more lightweight and this allows for larger shipments. This reduces the time it takes to get to the project
site.
•Metal roof trusses are fire resistant.
•They are compatible with almost all types of roofing systems.
•No insect infestations can occur.
•Chemical treatments are not necessary to maintain the trusses.
•Metal roof trusses are recyclable and therefore environmentally friendly.
Disadvantages of Metal Roof Truss Structures
•Skilled labor is required to install metal roof trusses.
•They are not energy efficient since they allow more heat to escape from the structure.
•Metal roof trusses allow sound to be more easily transmitted.
•Temperature fluctuations allow them to move more.
•When the metal is cut, drilled, scratched or welded, rust can become a problem.
•The workers have a higher risk of electrocution when installing the metal roof trusses.
•Wires that are on the trusses can rub over time creating a hazard to anyone who happens to touch the metal trusses.

Steel Trusses
Truss forms
7. King post truss:
It is the simplest form of roof truss, atriangular frame consisting
of two equal rafter members connected by a tie-beam.
The tie beam becomes necessarywhen the outward thrust of the rafters
is too great for the resistanceof the walls.
In aking post truss the bending moment on the tension member, dues to
its own weightand load of the ceiling, increasesas the span of the truss
increases. The section required to resist both the tensileand transverse
bending stresses would necessarily be large; hence, to reduce the size of
this membera suspension rod is introduced.
The king post is in tension, usuallysupporting the tie beam as a truss
but the crownpost is supported by the tie beam and is in compression. The
crown post rises to a crownplate immediately below and supporting collar
beams, it does not rise to the apex like aking post.
It is limitedto a spanof 24 feet.



Simple representation of aKing post truss


Representation of aKing post truss showing jointing

Steel Trusses
Truss forms
Steel roof trusses are availablein many differentforms and systems, the following may be used for steel roof trusses:
1. Fink truss:
The Fink truss offers greater economy in terms of
steel weight for
short-span high-pitched roofs as the members are
subdivided into shorter elements.
There are many ways of arranging and
subdividing the chords and internal members.
This type of truss is commonly used to construct
roofs in houses. when made of steel it is more
economical for long spans than either the howe or
the pratt.
Most types of roofing use a“W” pattern truss.
1/3 1/3 1/3

USING SIMILAR TRIANGLES, THE LENGTH (X) OF THE TOP CHORD IS DETERMINED. X/42 = 13.89/12
X = (42 X 13.89) 12 = 48.615” OR 4’ ⅝”. TRUSSES ARE BUILT ON A FLAT SURFACE AND THE PIECES
ARE CUT TO SUIT THE LAYOUT MARKS.
USES :
 FINK TRUSSES ARE USES FOR SHORT SPAN STRUCTURES
MAXIMUM 9’.
 TRUSSES ARE USED FOR PITCHED ROOF IN HOMES.
DISADVANTAGE :
 FINK TRUSSES ARE NOT USES FOR LONG SPAN (USE FOR ONLY
SMALL SPAN)

Steel Trusses
Truss forms
2. Queen post truss (Fan Truss): Principal Rafter
It is useful as a rectangular space is desiredin thecenterof the room,
an atticor small hall.
If the span lengthis in between8 to12 meter then queen posttrusses
are used.
Two vertical posts are provided in 2 sides at a distance whichare
termed asqueen posts.
Straining beam and strainingseal is used to keep the queen postsin exact
position.
Top endsof two main rafters are joined with thequeen postsheads. It
can be usedin longerspans when it is cross-braced in thecenter.
Double Fan
The fan truss has three or four members fanningout from a common
pointat the bottom of the truss.
The double fan has twocommon pointswheremembersfanout.





 Fan truss
3.


Double-Fan truss
4. Cambered Fink
 With Fink or Fan trusses having an inclination for the rafter not exceeding 30 degrees it is
more economical to employ a horizontal chord or tie since it obviates bending of the
laterals.
 Raising the bottom chord, also materially increases the strains in the truss members,
henceit increases the cost.
 A truss whose bottom chord has a rise of two or three feet, presents a better appearance,
however, than one with a horizontal chord, and for steep roofs, it will generally be fully as
economical toraisethe bottomchordbecause of the shorteningof the members.
 Trusses with raisedties are designated as“Cambered."
Queen Post

Steel Trusses
Truss forms
6. Howe truss:
The method of increasingthe number of triangles, as shown ,
may go on indefinitelyand the naturaloutcome is the howe truss. This
truss maybe extended to very large spans by increasingthe number of
panels, but it is not suitablefor steep roofs, because as the span
increases,the lengthof the struts towardthe centre becomes so great as
to requiretimberof large size. For long trussesthe usual rise is one-
seventh of the span. With long spans, it is customaryto reduce the shear
at the heel of the truss by placing the compressionmember nearest the
wall more nearly vertica
l.
The Howe Trusswas and sometimeseven now is used in steel bridges.
It's impressivestrength over long spanscontributedto its overwhelming
popularityas arailroadbridge.
The design of Howe truss is the oppositeto that of Pratt truss
in whichthe diagonal members are slanted in the direction
oppositeto that of Pratt truss (i.e. slantingaway from the middle
of bridge span) and as such compressiveforces are generated in diagonal
members.Hence, it is not economical to use steel members to handle
compressiveforce.
Simple representation of aHowe truss Representation of aHowe truss showing jointing

Steel Trusses
Truss forms
8. Pratt truss:
Pratt its similarity to the Howetruss, and the pointsof
difference readilynoted. In the Pratttruss, the compression members of
the web of the frame,or the struts a, a are vertical, while the tension
rods b, b are oblique.In the Howe, a reversed conditionexists, for the
struts are obliqueand the tension members vertical.
The Pratt offers rather a betterappearance than the Howe from the fact
that the oblique members, whichusually extend at differentangles, are
round bars that are hardly noticeable, but in the Howethey are made of
timbers, which are frequently unnecessarily heavy and far from pleasing
in appearance, while the verticaltimberstruts used in the Pratt arc
entirelyunobjectionable.
The howe truss, however,has the advantage that the connections at
c, d, and e are more conveniently made. The design uses vertical
members for compression and horizontalmembers to respond to
tension.


Simple representation of aPratt truss
Lateral (wind) bracing
Struts
Sway bracing

Portal strut
and bracing

Deck
StringersFloor beams
Representation of a Pratttruss showing jointing

Steel Trusses
Truss forms
9.


Flat Warren truss:
It is a typeof Parallel Chord truss.
Warren truss containsa series of isosceles triangles or equilateral
triangles. To increase the span lengthof the truss bridge, verticals
are added for Warren Truss.
The unique design of aWarren truss structureensures that no strut,
beam or tie bends or withstands torsional straining forces but is only
subject to tensionor compression. The loads on the diagonals alternate
between tensionand compression,whereas the elements near the
center are requiredto supportboth compression as well as tensionin
response to live loads. The use of the Warrentruss design is common
in prefabricated modular bridges wherein all the girders are of equal
length. Warrentruss is a notchbetter than Neville truss, which has
isosceles triangles filling up the entirelength of a bridgedesign.
Warren TrussAdvantages
- There is less material required for the constructionof aWarren
truss bridge.

Simple representation of aFlat warren truss


 - There is less blockage of view.
 - The constituents of aWarren truss bridgecan be assembledpiece wise.
Representation of a Pratttruss showing jointing

WARREN TRUSS ADVANTAGES
- THERE IS LESS MATERIAL REQUIRED FOR THE CONSTRUCTION OF A WARREN TRUSS BRIDGE.
- THERE IS LESS BLOCKAGE OF VIEW.
- THE CONSTITUENTS OF A WARREN TRUSS BRIDGE CAN BE ASSEMBLED PIECE WISE.
WARREN TRUSS BRIDGE DISADVANTAGES
- THE MAINTENANCE OF THE JOINTS AND FITTINGS OF A WARREN TRUSS BRIDGE COULD BE EXPENSIVE.
- THE CALCULATIONS TO DETERMINE THE LOAD-BEARING CAPACITY OF A WARREN TRUSS BRIDGE CAN BE
HASSLING.
- MANY WARREN TRUSS BRIDGES ARE NOT AESTHETICALLY APPEALING TO THE EYE.
- THERE COULD BE TOO MUCH DEFLECTION FOR LONG SPANS.

NORTH LIGHT TRUSS
 North light trusses are traditionally used for
short spans in industrial workshop-type
buildings. They allow maximum benefit to be
gained from natural lighting by the use of
glazing on the steeper pitch which generally
faces north or north-east to reduce solar gain.
On the steeper sloping portion of the truss, it
is typical to have a truss running
perpendicular to the plane of the North Light
truss, to provide large column-free spaces.
 The use of north lights to increase natural
daylighting can reduce the operational
carbon emissions of buildings although their
impact should be explored using dynamic
thermal modelling. Although north lights
reduce the requirement for artificial lighting
and can reduce the risk of overheating, by
increasing the volume of the building they can
also increase the demand for space heating.
Further guidance is given in the Target
Zero Warehouse buildings design guide .

SAWTOOTH TRUSS
A truss made with one top chord steeper than the
other, usually to add windows.
A variation of the North light truss is the saw-
tooth truss which is used in multi-bay
buildings. Similar to the North light truss , it is
typical to include a truss of the vertical face
running perpendicular to the plane of the saw-
tooth truss.
SPAN: 5m to 8m
MATERIAL : steel or timber

 Saw-tooth roofs may be constructed of heavy timber or steel trusses .
 This is generally used in factories where more light is required.
WIDELY USED TO SERVE TWO MAIN
FUNCTIONS:
To carry the roof load
To provide horizontal stability.

Light fills the space from clerestory windows in
the sawtooth-style roof
EXAMPLES
WINDOWS
green house with saw tooth roof truss

ADVANTAGES
 The major advantage of installing a saw-tooth roof truss on a structure is the
uniform diffusion of light throughout the space below it.
 Saw-tooth roofs prevent the influx of direct sunlight while providing
northern light.
 In saw-tooth design, every bay has an angled skylight. Less glare and
unwanted heat also offer better working conditions, increased production
 The complex design and various building materials needed will make the
sawtooth roof much more expensive than other roof types.
 It’s also a high maintenance roof.
 Adding windows, valleys and varying slopes creates a higher chance for
water leaks. For this reason, sawtooth roofs aren’t advisable in heavy
snowfall areas.
DISADVANTAGES
APPLICATIONS
o Lofts
o machine shops
o Warehouses
o factories
o Residences

SHELLS
THEORY OF STRUCTURES
GROUP MEMBERS
ANJALI KOLI
ANOUSHKA SHARMA
KANISHKA SHARMA
LIPIKA AGGARWAL
SHUBHAM GUPTA
TEJASVI KAUR

 A shell is a type of structural element which is characterized by its geometry, being a
three-dimensional solid whose thickness is very small when compared with other
dimensions. A shell structure is a thin, curved membrane or slab, usually of reinforced
concrete, that functions both as structure and covering, the structure deriving its
strength and rigidity from the curved shell forms.
 Essentially, a shell can be derived from a plate by two means : by initially forming the
middle surface as a singly or doubly curved surface and by applying loads which are co
planar to a plate’s plane which generate significant stresses. Shell structures
predominantly resist loads on them by direct compression. That is without bending or
flexure.
 Since most materials are more effective in compression than in bending, shell
structures result in lesser thickness than flat structures
TYPES:
 Single curvature shells, curved on one linear axis, are part of cylindrical or cone in the
form of barrel vaults and conoid shells.
 Double curvature shells are either part of a sphere, as a dome, or a hyperboloid of
revolution.
INTRODUCTION

THIN CONCRETE SHELLS
 The thin concrete shell structures are a lightweight construction composed of a relatively
thin shell made of reinforced concrete, usually without the use of internal supports giving
an open unobstructed interior. The shells are most commonly domes and flat plates, but
may also take the form of ellipsoids or cylindrical sections, or some combination thereof.
Most concrete shell structures are commercial and sports buildings or storage facilities.
There are two important factors in the development of the thin concrete shell
structures:
 The first factor is the shape which was developed along the history of these
constructions. Some shapes were resistant and can be erected easily. However, the
designer’s incessant desire for more ambitious structures did not stop and new shapes
were designed.
 The second factor to be considered in the thin concrete shell structures is the thickness,
which is usually less than 10 centimeters. For example, the thickness of the Hayden
planetarium was 7.6 centimeters.

• Shells belong to the family of arches, vaulted halls and domes. We can understand that a
vault is a shell with one singly curved surface and a dome is a shell with doubly curved
surfaces.
• A saddle shell has also doubly curved surfaces, but with a difference. If we cut a dome in
two directions at right angles to one another, both cuts are convex curves. If we cut a
saddle shell in the same way, one curve is convex and the other is concave.
• Examples ;
• Hyperbolic paraboloids and hyperboloids
• Shells are generally made out of reinforced concrete : from 40m (130 ft) to 73 m in
span. However, people have materialize the form of shells with space frames, lattices
and membranes, allowing larger spans (up to 200 meters.)

The Roman Pantheon, as it stands today in the centre of the city of Rome, really is a
remarkable and imposing structure. The Pantheon is a masterpiece of ancient shell
construction and has withstood for almost two-thousand years. Today, the span of 43 m still
impresses the engineering profession. The Pantheon, built in the early 2nd century A.C.,
approximately 125, is the largest unreinforced dome in the history.
HISTORY

• The membrane behaviour of shell structures refers to the general state of stress in a shell element that consists
of in-plane normal and shear stress resultants which transfer loads to the supports. In thin shells, the
component of stress normal to the shell surface is negligible in comparison to the other internal stress
components and therefore neglected in the classical thin shell theories. The initial curvature of the shell
surface enables the shell to carry even load perpendicular to the surface by in-plane stresses only.
• The carrying of load only by in-plane extensional stresses is closely related to the way in which membranes
carry their load. Because the flexural rigidity is much smaller than the extensional rigidity, a membrane under
external load mainly produces in-plane stresses. In case of shells, the external load also causes stretching or
contraction of the shell as a membrane, without producing significant bending or local curvature changes.
Hence, there is referred to the membrane behaviour of shells, described by the membrane theory.
• Carrying the load by in-plane membranes stresses is far more efficient than the mechanism of bending which is
often seen by other structural elements such as beams. Consequently, it is possible to construct very thin shell
structures. Thin shell structures are unable to resist significant bending moments and, therefore, their design
must allow and aim for a predominant membrane state. Bending stresses eventually arise when the
membrane stress field is insufficient to satisfy specific equilibrium or deformation requirements.
MEMBRANE BEHAVIOUR

Material Effects on Shell Behaviour
 Reinforced concrete shells have complicated nonlinear material behaviour with strong
influence on the structural behaviour. Significant tensile stresses in the shell will cause
cracking and with that weakening of the shell cross-section.
 Micro-cracking at the surface is caused by the evaporation of water. Due to the high
amount of surface exposed the micro-cracking in the shell surface may exceed the
allowable value.
 Furthermore, creep of concrete will cause flattening of the shell surface, resulting in
less curvature and possible bending stresses to occur. Additionally, shrinkage may lead
to unwanted residual stresses.

Cylindrical Shell Conical Shell
They may be of wood, steel, plastic or reinforced concrete.
They may form the roof and containing walls for long span structures.
Cylindrical Shell is a shell that is
a structure about an axis
parallel to the sides of an
imaginary straight sheet.
It distributes wind load equally
on the structure sides.
Conical Shell is a shell that is a
structure about an axis non-
parallel to the sides of an
imaginary straight sheet.
It is a stable structure for
standing high pressure winds.

The elements of a barrel shell are:
(1) The cylinder,
(2) The frame or ties at the ends, including the
columns, and
(3) The side elements, which may be a cylindrical
element, a folded plate element, columns, or all
combined.
For the shell shown in the sketch, the end frame is
solid and the side element is a vertical beam.
A barrel shell carries load longitudinally as a beam and
transversally as an arch. The arch, however, is
supported by internal shears, and so may be
calculated.
They maybe used as:
(1) Long-span structures
(2) Short-span structures
BARREL VAULTS

Cylindrical shell used in the roof are also known as barrel shell or vault

These may be of
multiple
numbers joined
together to
increase
strength

POSSIBLE METHODS OF JOINING CYLINDRICAL CONICAL SHELLS

SANGATH, AHMEDABAD
DELFT UNIVERSITY LIBRARY, NETHERLANDS

 A dome is an architectural element that resembles the hollow upper half of a sphere.
There are also a wide variety of forms and specialized terms to describe them. A dome
can rest upon a rotunda or drum, and can be supported by columns or piers that
transition to the dome through squinches or pendentives. A lantern may cover an
oculus and may itself have another dome.
 A dome is a rounded vault made of either curved segments or a shell of revolution,
meaning an arch rotated around its central vertical axis.
 Domes have a long architectural lineage that extends back into prehistory and they have
been constructed from mud, stone, wood, brick, concrete, metal, glass, and plastic over
the centuries. The symbolism associated with domes includes mortuary, celestial, and
governmental traditions that have likewise developed over time.
 The word "cupola" is another word for "dome", and is usually used for a small dome
upon a roof or turret. "Cupola" has also been used to describe the inner side of a dome.
Drums, also called tholobates, are cylindrical or polygonal walls with or without
windows that support a dome. A tambour or lantern is the equivalent structure over a
dome's oculus, supporting a cupola.
SPHERICAL DOMES

 As with arches, the "springing" of a dome is the point from which the dome rises. The
top of a dome is the "crown". The inner side of a dome is called the "intrados" and the
outer side is called the "extrados". The "haunch" is the part of an arch that lies roughly
halfway between the base and the top.
 A masonry dome produces thrusts down and outward. They are thought of in terms of
two kinds of forces at right angles from one another.
 Meridional forces (like the meridians, or lines of longitude, on a globe) are compressive
only, and increase towards the base, while hoop forces (like the lines of latitude on a
globe) are in compression at the top and tension at the base, with the transition in a
hemispherical dome occurring at an angle of 51.8 degrees from the top.
 The thrusts generated by a dome are directly proportional to the weight of its
materials. Grounded hemispherical domes generate significant horizontal thrusts at
their haunches.
 Concave from below, they can reflect sound and create echoes. A dome may have a
"whispering gallery" at its base that at certain places transmits distinct sound to other
distant places in the gallery.The half-domes over the apses of Byzantine churches
helped to project the chants of the clergy.
BEHAVIOUR

 When the base of the dome does not match the plan of the supporting walls beneath it
(for example, a dome's circular base over a square bay), techniques are employed to
transition between the two. The simplest technique used is diagonal lintels across the
corners of the walls to create an octagonal base.
 Another is to use arches to span the corners, which can support more weight. A variety
of these techniques use what are called "squinches". A squinch can be a single arch or a
set of multiple projecting nested arches placed diagonally over an internal corner.
Squinches can take a variety of other forms, as well, including trumpet arches and niche
heads, or half-domes.
 The earliest domes were built with mud-brick and then with baked brick and stone.
Domes of wood were allowed for wide spans due to the relatively light and flexible
nature of the material and were the normal method for domed churches by the 7th
century.
 Wooden domes were protected from the weather by roofing, such as copper or lead
sheeting. Domes of cut stone were more expensive and never as large, and timber was
used for large spans where brick was unavailable. Brick dome was the favoured choice
for large space monumental coverings until the Industrial Age, due to their convenience
and dependability.
TECHNIQUES & MATERIALS

 A grid shell is a structure which derives its strength from its double curvature but is
constructed of a grid or lattice.
 The grid can be made of any material, but is most often wood or steel.
 Grid shells were pioneered in the 1896 by Russian engineer Vladimir Shukhov in
constructions of exhibition pavilions of the All-Russia industrial and art exhibition 1896
in Nizhny Novgorod.
GRID SHELL DOME

 Louisiana Superdome, New Orleans
 Architect: Curtis and Davis
 Engineer: Sverdrup and Parcel
 With a 680 ft diameter the Louisiana
Superdome is the largest dome in existence.
 Designed for 75,000 spectators, the
multipurpose arena serves many functions
from various sports events to rock concerts
and political conventions.
 The patented lamella dome structure features
a peripheral tension ring truss.
A Tension ring
B Radial ribs
C Diagonal struts, parallel to radial ribs
D Hoop rings, combined with diagonal struts,
form a diamond bracing grid
E Roof joists
F Metal deck
G Single-ply water proof membrane
EXAMPLE

 Walter Bauersfeld built the first geodesic dome in
1922 for a planetarium in Jena, Germany.
Buckminster Fuller developed his geodesic dome
for low-cost housing 1942.
 A basic geodesic sphere, referred to as single
frequency, consists of 20 spherical triangles that
form pentagons. Dividing single frequency into
more units forms hexagons.
Frequencies: 1 2 3 4
GEODESIC DOME
1 Single frequency dome: 10 triangles forming
pentagons
2 Single frequency dome of 10 spherical triangles
3 Two-frequency sphere
4 Two-frequency hemisphere dome
5 Four-frequency hemisphere dome
6 Football of 10 hexagons, 12 pentagons

 US pavilion Expo 67 Montreal
 Architect: Buckminster Fuller & Shoji Sadao
 The 250 feet diameter by 200 feet high dome
roughly presents a three-quarter sphere, while
geodesic domes before 1967 were hemispherical.
The dome consists of steel pipes and 1,900 acrylic
panels. To keep the indoor temperature
acceptable, the design included mobile triangular
panels that would move over the inner surface
following the sun. Although brilliant on paper, this
feature was too advanced for its time and never
worked. Instead valves in the centre of acrylic
panels enabled ventilation.
EXAMPLE

 Climatron, Missouri Botanical Gardens, St Louis (1959)
 Architect: Murphey & Mackey
 Engineer: Paul Londe
 The dome of 175 feet diameter and 70 feet height permits tall palm trees to tower
above tropical streams, waterfalls and 1,200 species of exotic trees and plants.
 Temperature ranges 64 to 74 degrees and average humidity is 85 percent.
EXAMPLE

• Spruce Goose dome, Long Beach, USA
• Architect: R. Duell and Associates
• Engineer/builder: Temcor
• This aluminium dome for Hugh’s Spruce
Goose(at 415 ft diameter among the largest
geodesic domes). The dome of 15 geodesic
frequencies weighs < 3 psf.
• The design had to provide a temporary
opening for the plane of 320 ft wing-span to
pass through.
A Aluminium cover plate with silicone seal
B Aluminium gusset plates, bolted to struts
C Aluminium batten secure silicone gaskets
D Triangular aluminium panels
E Wide-flange aluminium struts
F Stainless steel bolts
EXAMPLE

HPR dome, Walla Walla, USA
Architect: Environmental Concern, Inc.
Engineer/builder: Temcor
Aluminum dome of 206’ diameter and 42 ft depth
(span/depth ratio 4.9), weighs less than 3 psf.
EXAMPLE

HYPERBOLIC PARABOLOID
 Formed by sweeping a convex parabola along a
concave parabola or by sweeping a straight line over a
straight path at one end and another straight path not
parallel to the first.
Structural behaviours
 Depending on the shape of the shell relative to the
curvature, theere will be different stresses.
 Shell roofs, have compression stresses following the
convex curvature and the tension stresses following
concave curvate.

PROPERTIES
 Hyperboloid structures are superior in stability towards
outside forces compared to "straight" buildings, but have
shapes often creating large amounts of unusable volume
(low space efficiency) and therefore are more commonly
used in purpose-driven structures, such as water towers
(to support a large mass), cooling towers, and aesthetic
features.
Water tank hyperbolical concrete
shell structure

MIAMI MARINE STADIUM
 Preserving the Miami Marine Stadium is a
cast-in-place concrete 100-meter long
building with an eight-section hyperbolic
paraboloid roof
 It is 33-meter wide with a cantilever of 20
meter over the stands; one third of the
structure is built on piers into the water.
 Used for motorboat racing and various
types of concerts on a floating stage.

CONCRETE SHELL
 The material most suited for construction of shell structure is CONCRETE because it is
a highly plastic material when first mixed with water that can take up any shape on
centering or inside formwork.
 Small sections or reinforcement bars can readily be bent to follow the curvature or
shells.
 Once cement has set and the concrete has hardened the R.C.C membrane or slab acts
a strong, rigid shell which serves as both structure and covering to the building.
RCC & STEEL STRUCTURE

TYPES AND FORMS
Folded plates
Barrel shells
Domes
Translation shell

CENTERING OF SHELL
 Centering is the term used to describe the
necessary temporary support on which the
curved R.C.C. Shell structure is cast.
 The centering of a barrel vault which is a
part of a cylinder with same curvature along
its length , is less complex.
 The centering of concoid, dome and
hyperboloid of revolution is more complex
due to additional labour and wasteful
cutting of materials to form support for
shapes that are not of uniform linear
curvature.

CONCRETE SHELL CONSTRUCTION
 Shells may be cast in place, or pre-cast off site and
moved into place and assembled. The strongest
form of shell is the monolithic shell, which is cast as
a single unit.
 Geodesic domes may be constructed from concrete
sections, or may be constructed of a lightweight
foam with a layer of concrete applied over the top.
The advantage of this method is that each section of
the dome is small and easily handled. The layer of
concrete applied to the outside bonds the dome
into a semi-monolithic structure.
 Monolithic domes are cast in one piece out of
reinforced concrete and date back to the 1960s. It is
cost-effective and durable structures, especially
suitable for areas prone to natural disasters.
Monolithic domes can be built as homes, office
buildings, or for other purposes.
Monolithic dome in Alaska

 Completed in 1963, the University of
Illinois Assembly Hall, located in
Champaign, Illinois was and is the first
ever concrete-domed arena. The design
of the new building, by Max Abramovitz,
called for the construction of one of the
world’s largest edge-supported
structures.
 The Seattle Kingdome was the world's
first (and only) concrete-domed multi-
purpose stadium. It was completed in
1976 and demolished in 2000. The
Kingdome was constructed of triangular
segments of reinforced concrete that
were cast in place. Thick ribs provide
additional support.

• Concrete shells are naturally strong structures, allowing wide areas to be spanned
without the use of internal supports, giving an open, unobstructed interior.
• The use of concrete as a building material reduces both materials cost and a
construction cost, as concrete is relatively inexpensive and easily cast into compound
curves.
• The resulting structure may be immensely strong and safe; modern monolithic dome
houses, for example, have resisted hurricanes and fires, and are widely considered to
be strong enough to withstand even F5 tornadoes.
• Very light form of construction, to span 30m shell thickness required is 60mm.
• Dead load can be reduced economizing foundation and supporting system.
• Aesthetically it looks good over other forms of construction.
ADVANTAGES

 Since concrete is porous material, concrete domes often have issues with sealing. If
not treated, rainwater can seep through the roof and leak into the interior of the
building.
 On the other hand, the seamless construction of concrete domes prevents air from
escaping, and can lead to buildup of condensation on the inside of the shell. Shingling
or sealants are common solutions to the problem of exterior moisture, and
dehumidifiers or ventilation can address condensation.
 Shuttering problem
 Greater accuracy in formwork is required
 Good labour and supervision is necessary
 Rise of roof may be a disadvantage.
DISADVANTAGES

The Market Hall in Leipzig, Germany (1929) by Franz Dischinger

Petroleum Coke Bulk Storage - Pittsburg, California
OPAC Consulting Engineers

FOLDED PLATES
Nikhita Khurana
Pulkit Chawla
Tanvi Yadav
Dhruv Khurana

INTRODUCTION
• FOLDED PLATES is one of the simplest
shell structure.
• They are more adaptable to smaller areas
than curved surfaces which require
multiple use of forms for maximum
economy.
• A folded plate may be formed for about
the same cost as a horizontal slab and has
much less steel and concrete for the
same spans.
• Folded plates are not adapted to as wide
bay spacings as barrel vaults.
SHELL STRUCTURE
FOLDED PLATE STRUCTURE
BAY WIDTH OF
FOLDED PLATES
BAY
WIDTH
OF
BARREL
VAULT

BEHAVIOUR
 Each plate is assumed to act as a beam in its own
plane, this assumption is justified when the ratio of
the span "length“ of the plate to its height“ width“ is
large enough. But when this ratio is small, the plate
behaves as a deep beam.
• When the folded plate is that with simple joint ,
which mean that no more than 2 elements are
connected to the joint.
• But when more than 2 elements are connected to
the joint, it can be named as multiple joint. The
width of any plate should not be larger than 0.25 its
length to be considered to act as beam.
• Actions of Folded plate due to loads :
1) SLAB ACTION : loads are transmitted to ridges by
the bending of plates normal to their planes.
2) BEAM ACTION : Loads are transmitted through
plates in their planes to diaphragms.
RIDGE

COMPONENTS
• The principle components in a folded plate structure are illustrated in the sketch below. They
consist of,
1) the inclined plates,
2) edge plates which must be used to stiffen the wide plates,
3) stiffeners to carry the loads to the supports and to hold the plates in line, and
4) columns to support the structure in the air.
• A strip across a folded plate is called a slab element because the plate is designed as a slab in that
direction.
• The span of the structure is the greater distance between columns and the bay width is the distance
between similar structural units.
• If several units were placed side by side, the edge plates should be omitted except for the first and last
plate.
• If the edge plate is not omitted on inside edges, the form should be called a two segment folded plate
with a common edge plate.
• The structure may have a simple span or multiple spans of varying length, or the folded plate may
cantilever from the supports without a stiffener at the end.
TAPERED FOLDED PLATES
Inclined plates
Edge plates
Stiffeners
Columns
Span

THE PRINCIPLE OF FOLDING
STRUCTURAL BEHAVIOUR OF FOLDING
• The inner load transfer of a folding structure happens through the twisted plane, either through the
structural condition of the plate (load perpendicular to the centre plane) or through the structural
condition of the slab (load parallel to the plane).
• At first, the external forces are transferred due to the structural condition of the plate to the
shorter edge of one folding element.
• There, the reaction as an axial force is divided between the adjacent elements which results in a
strain of the structural condition of the slabs. This leads to the transmission of forces to the bearing.

FORMS OF FOLDED PLATE STRUCTURES• By using folded structures different spatial
forms can be made.
• The straight elements forming a folded
construction can be of various shapes:
rectangular, trapezoidal or triangular.
• By combining these elements we get
different forms resulting in a variety of shapes
and remarkable architectural expression.
• Folded structures in the plane are the
structures in which all the highest points of
the elements and all the elements of the
lowest points of the folded structure belong
to two parallel planes.
• Frame folded structures represent
constructional set in which the elements of
each segment of the folds mutually occupy
a frame spatial form. This type of folded
structure is spatial organization of two or
more folds in the plane.
• Spatial folded structures are the type of a
structure in which a spatial constructive set is
formed by combining mutually the elements
of a folded structure.

FORMS OF FOLDED PLATE STRUCTURES
• The shape of folded structures affects the transmission of load and direction of relying of folded
structures. Based on these parameters, folded plate systems are further classified into :
1. linear folded plate structure
2. radial folded plate structure
3. spatial folded plate structure
LINEAR FOLDED
PLATE STRUCTURE
RADIAL FOLDED
PLATE STRUCTURE
SPATIAL FOLDED
PLATE STRUCTURE
• Combined folded constructions are carried out over the complex geometric basis, formed by the
combination of simple geometric figures, rectangles and semicircles on one side or both sides.
• This type of folded structure can be derived in the plane or as a frame (cylindrical) structure, and
represents a combination of folded structure above the rectangular base and ½ of the radial
construction.
EXAMPLE OF A COMBINED FOLDED
STRUCTURE FORMED BY A CYLINDRICAL
FOLDED STRUCTURE AND HALF OF DOME
STRUCTURE

TYPES OF FOLDED PLATE STRUCTURES
 LONGITUDINAL/ PRISMATIC FOLDING
• Longitudinal folding is characterized through uninterrupted
and linked folding edges where parallel and skew up folds and
down folds alternate.
• Single-layered longitudinal folding corresponds in their load
bearing structure to a linear load bearing system whereas a
double-layered folding with different directions of their folds
can create the structural condition of the plate.
 SPOT OR FACET FOLDING
• Also called spot or facet folding, requires that several folds
intersect like a bunch in one single spot. This results in pyramidal
folds with crystalline or facet-like planes.
• Facet folding can either be based on a triangular shape or on
a quadrangular shape.
• A single or double-layered facet folding resembles the load
bearing structure of a plate and can be compared to space
frameworks
SKETCH PYRAMIDAL FOLDING
SKETCH LONGITUDINAL FOLDING

•Reinforced Cement Concrete
•Steel Plate
•Mixture of Concrete and lightweight terracotta tiles
•Polymer mixture of concrete and fibreglass
•Scored laminated timber sheets
•Prestressed concrete folded plates
•Extremely light with concrete thickness of 200mm
•An existing hangar at Santa Cruz Airport, Mumbai
(Bombay), India, has been extended to accommodate
additional aircraft and engineering facilities.
•Contains 8 folds
•62 m long cantilever of the new folded-plate roof
• Measure152 x 60 m in plan, and is symmetrically
divided by a longitudinal expansion joint
•The 152 m length consists of two cantilevered roofs,
each 62.3 m long, and a central roof 27.4 m long over
the maintenance building.
•Highest point of roof is 32.3m above ground
•The transverse section of the folded plate consists of
eight 7.6 m wide modules, each having a corrugated
plate arrangement, with horizontal top and bottom
plates inclined at 45° between the webs.

EXAMPLE: THE CHURCH OF NOTRE DAME, THE
CITY OF ROYAN
•Walls can be designed and carried out as folded
structures, since by folding we get a solid
construction that can accept large vertical and
horizontal impacts, which enables exceptional
height of the wall fabric.
•This type of folded structures, due to their
geometry, provides an economical solution and
the rational use of material when compared to
the height of the building.
•Walls made as folded structures can be
materialized in reinforced concrete.
•Facility constructed with this structure is the
church of Notre Dame, the city of Royan, France,
1958, with the walls built in the form of folded in
"V" shape of reinforced concrete.
•Viable galleries, which have a constructive role
of the diaphragm, are built on them

• since they are of concrete, such roofs have inherent resistance to fire, deterioration and to
atmospheric corrosion.
• They allow large spans to be achieved in structural concrete. This allows flexibility of planning and
mobility beneath.
• Where ground conditions require expensive piled foundations the reduced number of supporting
columns can be an economic advantage.
• The plates are required to be thicker than the shells, and there are more firms who will tackle
constructing them without excessive prices, increasing competition and sometimes making the
cost more competitive than for cylindrical shells.
 DISADVANTAGES
• Skilled labor is required in the construction of curved shuttering.
• Since concrete is porous material, concrete domes often have issues with sealing. If not treated,
rainwater can seep through the roof and leak into the interior of the building
• Labor skilled in curved shuttering are very expensive
• Skilled labor for folded plates are hard to find
 ADVANTAGES
•Storage buildings
•Swimming pools
•Gyms
•Airports etc.
 USES

APPLICATION
• Folded structures have found the application in
architectural buildings and engineering structures.
• Based on the position in the architectural structure, this
type of construction can be divided into: roof, floor and
wall folded constructions.
• The largest number of examples of folded structures are
roof structures.
• The need for acquiring the larger range and more cost
effective structure led to the emergence of this type of
structure.
• The largest application of folded structures is in the
formation of trapezoidal sheet.
• This type of folded structure can absorb and receive the
load without introducing additional structure.
• Application of trapezoidal sheet, except as roofing, is in
making the thermal insulation of roof and wall sandwich
panels.

HIGH RISE
BUILDINGS
PRESENTED BY :
•KARTIK KUMAR
•PAYAL GUPTA
•PRACHI ARORA
•MEGHA KASHYAP
•NEETU SHARMA
•ARJUN
•MOHIT GUPTA

INTRODUCTION AND DEFINITION
High rise is defined differently by different bodies.
Emporis standards-
“A multi-story structure between 35-
100 meters tall, or a building of
unknown height from 12-39 floors is
termed as high rise.
Building code of Hyderabad,India-
A high-rise building is one with four
floors or more, or one 15 meters or
more in height.
The International Conference on Fire
Safety –
"any structure where the height can
have a serious impact on evacuation“
U.S., the National Fire Protection
Association
A high-rise as being higher than 75 feet (23
meters), or about 7 stories

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