STRUCTURES
DEFINITION
A structure is something that consists of many parts
held together in a specific way
 We see and use many different types of structures every day, each with its own
function.
 Structures give us shelter, spans gap and supports loads.
 Structures include things like bridges, electricity towers, traditional huts and highrise buildings.
 Some structures are old and famous like Zimbabwean ruins and Egyptian pyramids.
 Others are new like Nelson Mandela Bridge in Johannesburg and the Cape Town
Stadium in Green Point.
PURPOSE OF STRUCTURES
Structures are made or constructed for different reasons. Most structures have several
functions, which include:
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To contain things or objects
To protect and shelter object
To carry things
To support loads
To span a distance
In order to resist force and to avoid structural failure all structures must be:
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Strong (unable to break or collapse)
Rigid (unable to bend or change shapes)
Stable (unable to fall over)
Classification of structures
Structures can be classified into two groups, namely:
Natural structures
Man-made structures
Structures that are
not made by people
and that occur in
nature
Structures that
have been
constructed by
people.
Examples of natural structures
 Trees
 Plants
 Rock formations
 Caves
 Skeletons and bones
 Feathers of birds
Examples of man-made structures
 Tent
 Buildings
 Pylons
 Bridges
 Ladder
 Bench
Types of structures
Frame structures
Frame structures are made
from beams connected to each
other to support a load.
Sometimes the framework is
hidden as it protects the
structure from the inside.
Examples:
 Skeleton
 Birdcage
 Steel frame
 Timber frame
Shell structures
Shell structures are structures that
have a solid outer surface, like skin
covering your body.
- Not composed of different
parts, but it is one whole piece.
- It does not have a frame as a
support as the shell itself acts
as the support.
- Lighter in weight than a frame
structure.
Examples:
 Car body
 Snail shell
 Can
 Eggshell
 seashells
Solid structures
Solid structures are rigid
and heavy
Solid structures are not
made of different parts but
are “one form” structures.
They do not take the shape
of the container and they
are not compressible.
Examples:
 Column
 Stone pillar
 Concrete walls
 Mountains
 Bricks and stones
Investigate a frame structure: a cell phone tower
KEY WORDS
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Tie beam – a horizontal
beam or crosspiece in a
frame structure that
supports the other
members by holding or
pulling sections
together.
Tension force – a type
of force that stretches a
member.
Strut – a diagonal rod
or bar in a frame
structure that braces or
supports the other
sections and keeps
them in position by
pushing against them.
Compression force – a
type of force that
squashes a member.
Structure of a cell phone tower
Frame structures consist of many rigid members that are joined
together to form the structure. These members are usually
beams. The beams have different names depending on their
location and function in the structure.
Similarities in frame structures
When you look at different frame structures, you will notice that they share some similar
features. These similarities help to strengthen the structure and enable the different
sections of the structure to resist the forces acting on them.
A cell phone tower consists of different beams and struts that withstand tension and
compression forces. Most cell phone towers have the following in common:
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They have wide bases that help to stabilize them.
The tower members are held together using cross pieces. These are called tie beams and
support the members by holding or pulling on them (tension force).
Sections of the towers are held in position by beams called struts. These struts are
diagonal members that support the sections by pushing against them and keeping them
in position (compression force).
The triangular shapes in these towers are very noticeable. A triangular frame is very
strong. Many structures and buildings use this shape in their construction.
Strengthening Structures
KEY WORDS
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Triangulation – refers
to arranging members
in triangular shapes in
order to make frame
structures stronger.
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Pylons – tall frame
structures made from
strong materials to
help it carry or hold
heavy objects.
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Mine headgear – tall
frame structures built
over mine shafts to
hold the machines
that transport people
and equipment into
the mine.
If you look at frame structures like cell phone towers and
wind structures, you will see a lot of triangular shapes in their
structures.
To strengthen frame structures, we use a method called
triangulation.
Triangulation is used to strengthen many types of frame
structures including:
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Pylons – pylons are large frame structures made from
very strong materials that are used to support heavy objects
such as power lines.
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Wind structures – these are tall frame structures that
convert wind energy into usable energy. The wind turns the
blades, which operate a machine that can be used to grind
grain into flour (windmill), pump water from an underground
water source (wind pump) or generate electricity (wind
generator).
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Mine headgear – these are steel frame structures that
are constructed over mineshafts. They are used to support
the machines that transport mine workers and materials in
and out of underground mines.
A wind generator
A pylon
Mine headgear
The Impact of Technology
Evaluating landline telephone systems
 Technology offers a range of communication
products that use both landline and mobile (cell)
telephone systems.
 Landline telephones send signals through a network of cables which are either buried in
the ground or suspended in the air.
Advantages of landline telephone systems
Landline telephone systems have these advantages:
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Reliability – because they rely on wires to transmit signals, landline telephones are
more reliable than mobile phones.
Emergencies – because landline telephones are reliable, you need not worry about
poor reception in emergency situations.
Price – landline telephone calls are cheaper than cell phone calls.
Disadvantages of landline telephone systems
Landline telephone systems have these disadvantages:
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Cable theft – when cables are stolen or broken, no telephone service is available.
Mobility – because landline telephones require a physical, fixed connection, you can
only use them where they are. The reception of a landline telephone is determined
by the length of its attached cord to the handset or the range the cordless telephone
can receive a signal.
Availability – some remote areas in South Africa don’t have the infrastructure for
landline telephones.
Long distance charges – call charges are determined by the distance and duration of
the call.
Evaluating mobile telephone systems
Mobile phones (cell phones) connect to a cellular network and transmit
signals using radio waves.
Advantages of mobile telephone systems
Mobile telephone systems have the following advantages:
 Ease of communication – anyone in the world who is not close to a landline
telephone, but has a cell phone and reception, can be called.
 No long distance charges – call phone usage is charged by the minute,
regardless of where the user calls from (except for international calling).
 Safety – having a cell phone means you can always call for help when you
need it, even if you are walking down the road or sitting in a moving car.
Disadvantages of mobile telephone systems
Mobile telephone systems have these disadvantages:
 Interruption – cell phones can be disruptive! You can be called anytime and
everywhere.
 Safety – talking on a cell phone can distract you from other (daily) activities
and tasks.
 Service – bad weather or software glitches can cause fuzzy reception or can
cause calls that are in progress to disconnect.
 Availability – some remote areas in South Africa do not provide cell phone
coverage.