Design of long span floor system

Department of Civil Engineering
University of Engineering and Technology
Taxila, Pakistan
Presented To:
Professor Dr. Muhammad Yaqub
Presented By:
Khadim Hussain 2K17-MS-STR-FT-07
Rana Dilawar khan 2K17-MS-STR-PT-02
M. Farrukh Javaid 2K17-MS-STR-PT-11
STRUCTURAL DESIGN PRACTICE
Design of Long Span Floor System

1. Introduction to Long Span Floor System
2. History and Evolution of Long span Floor System
3. Classification of Long Span System
4. Material for long span structures
5. Common Structural Forms for Long Span
6. Conclusion
Contents
3Department of civil Engineering, University of Engineering and Technology, Taxila

Introduction
Visibility Flexibility Large Scale Storage
Auditoriums
Stadiums
Exhibition halls
Manufacturing facilities
Aircraft hangars
 Long span structures create unobstructed, column-free spaces
greater than 30m (100 feet) for a variety of functions.

 Dated back to the Roman civilization However, most long-span
buildings then were single level constructed using vaults and
domes.
 By the late 20th century, durable upper limits of span were
established for these types:
 The largest covered stadium had a span of 204 meters (670 feet).
 The largest exhibition hall had a span of 216 meters (710 feet).
 And the largest commercial fixed-wing aircraft had a 75–80 meter
(250–266 foot) span hangar.
 In these buildings the structural system needed to
achieve these spans is a major concern.
History and Evolution

History and Evolution
The major evolution in long span section- active structures has
occurred in the aspect of shift from in-situ to precast construction
Old-to-New long span structures
with their height and spans

Classification
Department of civil Engineering, University of Engineering and Technology, Taxila
7
 One way to classify long-span and complicated structures
 Form active systems
 Vector active systems
 Section active systems
 Surface active systems

 Form active structural systems are systems of flexible, non-rigid
matter, in which the forces is carried by the form and type of
material.
Example of structures:
1. Cable structures
2. Tent structures
3. Pneumatic structures
4. Arch structures
Form active structural systems

Place/Country: Berlin/Germany; Completion: 2000; Business area:
Steel-Glass- Structure; Type: Cable Structures
Place/Country: Berlin/Germany; Completion: 2000; Business area:
Steel-Glass- Structure; Type: Cable Structures
Place/Country: Berlin/Germany; Completion: 2000; Business area: Steel-
Glass- Structure; Type: Cable Structures
Place/Country: Berlin/Germany; Completion: 2000; Business area: Steel-
Glass- Structure; Type: Cable Structures

Pneumatic structures
Air-inflated system air pressure
30–700 kN/m2 (common used)

Tent structures
Khalifa International Stadium to feature tensile roofing system

Arch structure

Vector active structural systems
 Vector active structural systems are systems of solid, straight
linear members, in which the redirection of forces is effected by
vector partition, i.e. by multidirectional splitting of single force
simply to tension or compressive elements
Example of structures:
1. Flat trusses
2. Curved trusses

Flat trusses

Curved Truss

 Section active structural system are systems of rigid, solid, linear
elements, in which redirection of forces is done by structural
member’s section and their load transferring efficiency.
 Example of structures:
1. Frame structures
Section active structural systems

Frame structures

 Surface active structural systems are systems of flexible or rigid
planes able to resist tension, compression or shear, in which the
redirection of forces is done by curved geometry in 3 dimension.
 Example of structures:
1. Folded plates structures
2. Shell structures
Surface active structural systems

THE LEIPZIG MARKET HALL
Leipzig, Germany
1929
Span: 68.5 m
Reinforced concrete shells

Folded plate structures

Kamalapur Rail Station
Bangladesh

Materials suitable for various forms of
long span
1.All reinforced concrete including precast
2. All metal (e.g. mild-steel stainless steel or alloyed aluminum
3. Timber
4. Metal/RC combined
5. Plastic-coated Textile material
6. Fiber reinforced plastic
24
24

Common Structural Forms for Long Span
Building Structures
Common Structural Forms for long span structures are
1. Insitu RC
2. Precast concrete
3. Structural steel – erected on spot
4. Structural steel – prefabricated and installed on spot

Common Structural Forms for Long Span
Building Structures
5. Cable suspended structures
6. Inflated structures
7. Shell structures
8. Folded plate structures
9. Dome structures

27
LIMITATIONS
Arch: H/S ratio
Truss: Heavy Material
Shell: Surface Geometry
Cables: Wind,Vibration,Moving Loads
Pneumatic: Mechanical Failure

Shell Structures
28
28

Shell Structures
 Shell is a type of building enclosures.
 Shells belong to the family of arches .
 They can be defined as curved or angled structures capable of
transmitting loads in more than two directions to supports.
 A shell with one curved surface is known as a vault (single
curvature).
 A shell with doubly curved surface is known as a dome (double
curvature).

Classification of shells
 There are many different ways to classify shell structuresbut two waysare
common:
1. Based on the material which the shell is made of like reinforced
concrete, plywood or steel, because each one has different properties
that can determine the shape of the building and therefore, these
characteristics haveto be considered in the design.
2. Basedon thickness: shells canbe thick or thin.

Thin Concrete Shells
There are two important factors inthedevelopment of thethin
concrete shellstructures:
 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 lessthan 10 centimeters. For example, the
thickness of the Haydenplanetarium was7.6centimeters.

Barrels shells
 The cylindrical thin shells, also called
barrels, should not be confused with
the vaults even with the huge
similarity in the shape of both
structures, because each of these
structures has a different structural
behavior as well as different
requirements in the minimum
thickness and the shape.

 On one hand, the structural
behavior of the vault is based on
connected parallel arches, which
transmit the same effort to the
supports .
 Therefore, the materials used in
these structures have to be able to
resists compressions (e.g. stone)
and the thickness is usually higher.
Furthermore, the shape of the
vaults must be as similar as
possible to the arch in order to
achieve the optimum structural
behavior.

 On the other hand, the structural behavior of
the barrels shell is that it carries load
longitudinally as a beam and transversally as
an arch. and therefore, the materials have to
resist both compression andtension stresses.
 This factor takes advantage of the bars of the
reinforced concrete, because these elements
can be placed where tension forces are needed
and therefore, the span to thickness Ratios can
be increased. Furthermore, the shapehasfewer
requirements than the vaults and therefore,
new curves like the ellipse or the parabola can
be used improving the aesthetic quality of the
structure

Advantages and Disadvantages of Shells
 ADVANTAGES
 Verylight form of construction.
 To span 30.0 m shellthicknessrequired is60mm
 Dead load can be reduced economizing foundation and supporting
system
 They further take advantage of the fact that arch shapes can span
longer
 Flat shapes by choosing certain arched shapes
 Esthetically it looks goodoverother forms of construction
37

Advantages and Disadvantages of Shells
 DIS-ADVANTAGES:
 Shuttering problem
 Greateraccuracy in formwork isrequired
 Good/Skilled Labour and supervisionnecessary
 Rise of roof may be a disadvantage
38

Folded Plates
 Athin-walled building structure of
the shell type.
 Folded plates are assemblies of flat
plates rigidly connected together
along their edges in such a way
that the structural system capable
of carrying loads without the need
for additional supporting beams
along mutual edges.
Engineer Eudene Freyssinet performed
the first roof with thefolded structure
in 1923 asan aircraft hangar at Orly
Airport inParis.

Folded Plates
FOLDING SYSTEMSIN NATURE
The principle of folding as a tool
to develop a general structural
shape has been known for a long
time.
Folded structure systems which are
analogous to several biological
systems such as found at broad
leaf-tree leaves, petals and foldable
insect wings, are adopted to be
employed in anew, technical way
40
Leafof PalmTree
Beetle InsectWith
FoldableWings
Seashell

Folded Plates
The structural characteristics of
folding structures depend on:
 Thepattern of thefolding.
 Their geometrical basicshape.
 Its material.
 Theconnection of the differentfolding planes
 Thedesign of the bearings.
 Movable form work canbeemployed.
 Form work required is relatively simpler.
 Design involves simpler calculations.
41

Folded Plates
Structuralbehavioroffolding
42
 Load Distribution process:
 At first, the external
forces are transferredto
the shorter edgeofone
folding element.
 There, the reaction asan
axial force is divided
between the adjacent
elements.
 Thenthe forces transferred
to thebearings. StructuralConditionOf Foldingstructures

Folded Plates
Classificationof folded structuresbasedonthe material they are
made of:
 Folded structures made of reinforced concrete
 Metal folded structures
 Folded structures of wood
 Folded structures of glass
 Folded structures of plastic materials
 Folded constructions made in combination of different
materials
43

Folded Plates Types
TYPESOFFOLDEDSTRUCTURE
Basedon geometric shapefolded structures canbe divided
into:
 Folded plate surfaces structures :
1. Prismatic: Rectangular plates.
2. Pyramidal: Non-rectangular plates.
3. Prismoidal: Triangular or trapezoidal plates
 Folded plate frames structures
 Spatial folded plate structures
44

Folded Plates Types

Folded Plates Types
GEODESICDOME
FOLDEDPLATERIGIDFRAME
TAPERED FOLDED PLATES

Folded Plates Types
THEAPPLICATIONOFFOLDEDSTRUCTURES
47
AsRoofStructure
Miami Marine Stadium,Florida
AsWallStructure
Church of Notre DamedeRoyan, France

Folded Plates Types
FOLDED PLATE HUT-JAPAN
48

Advantages and Disadvantages of Folded
Plates
49
Advantages
 Dead load can be reduced economizing foundation and supporting
system
 Theyfurthertakeadvantageofthe fact that archshapes can span longer
 Flat shapesby choosingcertain archedshapes

Advantages and Disadvantages of Folded
Plates
Disadvantages:
Shuttering is difficult.
Greater accuracy in formwork is required.
Good labor and supervision necessary.
Rise of roof may be a disadvantage.
50

Domes
52
Thedome is essentially an arch rotated around acenter
point 180 degrees, "...a group of archesconjoinedradially
around avertical axis"

Domes
53
Materials usedto construct
Bricks,mud, stone, glass,wood, metal, plastic
and concrete

Domes
54
MUD STONE
METAL CONCRETE

Domes
 Some of the terminology that isoften associated with domes
include
 Apex: the uppermost point of a dome (also known as the ‘crown’).
 Cupola: a small dome located on a roof or turret.
 Extrados: the outer curve of a dome.
 Haunch: part of an arch that that lies roughly halfway between the
base and the top.
 Intrados: the inner curve of a dome.
 Springing: the point from which the dome rises
57

Examples of Domes
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Epcot Center, Orlando, 1982

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Taj Mahal (1647, Quing Dynasty), Agra, India, 125 ft (38 m) span
corbelled dome

Advantages of Domes
 Reduces slab curling and shrinkage cracks, providing a higher
quality surface.
 Provides an under-slab void for running cables and pipes,
simplifying post-construction installation of new wiring and
utilities.
 Allows forming of complete structural suspended slabs on beam
pile foundations.
 Can be designed to create under-slab water reservoirs for storm
water management and fire suppression water storage.
60

Disadvantages of Domes
The major and simplest disadvantage one can think of is
that domed roof doesn't allow to go beyond ground floor
 A non accessible roof is very less preferred
Maintenance of domed roof is difficult
Difficult to carry out roof top installations , for eg. setting
of water storage tanks at top or maintenance room for lifts
61

Conclusion
These structures are preferred as having following
features
These structural systems reduce the loads on buildings.
Light weight.
Conventional system.
Economy.
Geometry.
62

Design of long span floor system

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