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SHELL STRUCTURE
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structure that surrounds something else
is a continuous surface structure
can usually be understood as a set of beams, arches
and catenaries
keep their shape and support loads, even without a
frame, or solid mass material inside
use a thin, carefully shaped, outer layer of material, to
provide their strength and rigidity.
D e f i n i t i o n
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a thin, curved plate structure shaped to
transmit applied forces by compressive, tensile,
and shear stresses that act in the plane of the
surfaces.
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T y p e s : classified by its /curveSingle curvature singly curved shells :
are curved on one linear axis and are part of a cylindeor cone
Type of single curvature shells :
1) Long Barrel Shell / Rampant Vault
2) Short Barrel Shell / Conical Vault
Double curvature doubly curved shells :are either part of a dome or a hyperboloid or revolutio
Type of double curvature shells :1) Hyperbolic Paraboloid
2) Rotational Shell : - Dome
- Hyperboloid
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LONG BARREL SHELL :
the span is large in
comparison to the width
Single curvature shells
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SHORT BARREL SHELL :
length is short than the width
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UPPER/TOP
PART IS IN
COMPRESSION
BOTTOM PARTIS IN TENSION
L o a d D i s t r i b u t i o n
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HYPERBOLIC PARABOLOID :
- is doubly curved
- a set of arches in one direction and a set
of cables, or inverted arches, in the other.
Double curvature shells
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L o a d D i s t r i b u t i o n
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DOME
- surfaces of revolution created by revolving
a curved line about an axis
- spherical : common dome; surface is
generated by rotating an arc of a circle
around a vertical axis
Rotational Shell
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COMPRESSION
TENSION
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L o a d D i s t r i b u t i o n
COMPRESSION
TENSION
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HYPERBOLOID
straight-line generator isskewed relative to plane
of circular paths
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COMPRESSION
TENSION
L o a d D i s t r i b u t i o n
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L o a d D i s t r i b u t i o nThe shape of a shell structure spreads forces
throughout the whole structure, which meansevery part of the structure supports only a small
part of the load, giving it its strength.
resist loads on them by direct compression -without bending or flexure.
Its efficiency is based on its curvature (single or
double),which allows a multiplicity of alternatives
tress paths and gives the optimum form for
transmission of many different load types.
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L o a d D i s t r i b u t i o n
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S t a b i l i t y
from its geometrical size
Interaction between shells
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Most suited: concrete reinforced with steel
mesh.
Alternative materials : plywood, metal,
glass-reinforced plasticas shell in boat
and automobile construction
M a t e r I a l
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Attraction of elegant simplicityof curved shell forms that utilize
the natural strength and
stiffness of shell formgreat economy in the use of
material.
Continuity and Curvature -The essential ingredients of a
shell structure
A d v a n t a g e s
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cost of labour, the construction of centering of
shell is very high.A tiny weakness or imperfection on the covering
can cause the whole structure to fail.
When the shell is formed from hot or moistmaterials, uneven cooling can cause some parts to
weaken other parts by pushing or pulling on
nearby sections.
Flat materials are difficult to form into the
rounded shell shape.
Assembly of flexible materials is very precise, so
that seams are strong where the pieces are joined.
D i s a d v a n t a g e s
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T H E E N D