The Design & Technology Department
An introduction to
Design and Make a Bridge
1
Year Seven
What is a Structure?
Structures are things which have been put together.
There are a number of features which are common to all
structures and they are:
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They are an arrangement of parts.
They must be able to carry loads for which they are
designed.
They must not collapse in use.
Some examples of different types of structures include:
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Houses
Chairs
Tables
Cranes
Aeroplanes
Thinking Skills
In your design booklet, write down as many
structures as you can think of.
2
STRUCTURES CAN BE DIVIDED INTO TWO MAIN GROUPS:
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FRAME STRUCTURES
SHELL STRUCTURES
THEY CAN BE EITHER NATURAL OR MAN MADE
NATURAL STRUCTURES
Like many other things in the world structures are not new.
Nature has been producing structures for many millions of
years. For example: Leaves, Spiders Webs, Bees Honeycomb.
SHELL STRUCTURES
Tins or cans, cars and aeroplanes are shell structures. There
are some structures which appear to be frame structures but
on examination are found to be frame structures made from
shell structures.
FRAME STRUCTURES
Some types of bridges are frame structures. They can
support their own weight and the weight of cars passing over
them.
REMEMBER
Structures are supporting frameworks, they must not collapse. There are many kinds of structures, natural ones and man made
ones. Each kind of structure has a special purpose. Think about: SUPPORT, SHELTER, and TRANSPORT!
3
FORCES
A force can be either static or dynamic. If you sit on a chair this is called a static force. If you swing on a chair this is
known as a dynamic force.
Forces however are not all the same. They can press, pull, twist or bend.
Compression – A force that squashes is said to be a compressive force.
Twisting – Is when you twist the top off a jar.
Bending – Is simply the force which tries to bend something.
Tension – If we pull in opposite directions then this is a tensile force.
Shear – When two opposite forces cut something.
4
TASK: Building a Hangman Structure
Use lengths of 10mm square timber and pieces of card to build a structure similar to the one shown in the drawing below.
You can make a series of additions to the structure to make it stronger, by adding extra pieces of timber. Remember, that
the more timber that you use, the more it will affect the ‘cost effectiveness’ of your hangman structure.
Task
In your design folder produce three different ideas for your hangman structure. Annotate each design and state which
one you are going to manufacture and why.
5
Making Structures
There are many different materials that can be
used to make structures. However, for our bridge
we are going to use either softwood or hardwood.
You have the opportunity to choose. You will fix
your structure together using a glue gun and card
to add strength.
Because of the cross sectional measurements of
the wood it is impractical to cut joints. Therefore
we will be using butt joints.
The strength of any butt joint is largely
dependent on the size of the area that comes into
contact with the glue. It can be frustrating
attempting to glue small sections together to make
a framework, and sometimes parts may be harder
to glue than others.
Look at the drawings on the left and you will see
how card can be added to the joints to make them
stronger.
6
Design and Make a Bridge
Bridges, what would we do without them? Most of us have travelled over, or under a bridge on the way to Y Pant School
today. Can you think where?
Consider?
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What type of bridges can we find locally?
Why are they built as they are?
What is the most famous bridge that you can think of?
What is special about this bridge?
We are going to design and make a bridge which will use our knowledge of structures, to make it strong and light.
TASK
Your task is to design a bridge using 10mm square timber, as you did with the hangman structure. It will span a gap of
500mm.
You will follow the design process using your project work booklet. This will enable you to produce a successful product.
While you are designing you should consider sensible and economical ways of using the materials.
In the plan you will need to calculate the cost of your bridge – the timber costs 1p for every 10mm. When the bridges are
tested we will be able to work out the most efficient bridge by relating the cost to the weight held by it.
7
The Brief
Design a Bridge that will span a
gap of 500mm.
Constraints
You are allowed a maximum of
5000mm of timber, which will
be 10mm square.
No other material may be
used. You will be either
working in teams of 2 or
working independently
depending on what your
teacher decides.
Jointing can be either with
card corners or butt jointing.
8
Design a bridge to span a distance of 500mm. It should be
between 50 and 75mm in width.