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Structures
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Type study
This section provides an analysis of the type of structure used in
building a bridge, a building and in making a parasol. It is followed
by an explanation of the elements used in each one.
a)
The case study of the bridge involves a modern viaduct or
bridge built over an old one. We begin with a breakdown of
each part and an analysis of their structural type. This will help
students to clearly identify each type and analyse the elements
they are made up of.
Taking the old bridge first, this is a solid structure built of an
accumulation of materials, specifically stone and brick. It has a
central arch which allows water to run through.
The viaduct situated at the top of the photo is made of the
following: the prefabricated concrete columns and the metal
triangular beams. Triangular beams make it possible to span
greater distances using less material, making for a lighter
structure
b)
The second case study shows two types of structures:
In the foreground there is a suspended structure showing vertical
metal supports that resist compression. These have a stretched
canvas as a cover and two tension cables which resist tension stress.
In the background there is a laminate structure. The eight laminates
are able to support their own weight because of their parabolic
curves. These bear compression stress.
Function study
This section explains how a structure works, and the different
elements according to the loads that they have to bear. We look
at how the loads of a structure affect each of their elements,
and how they would become deformed if they didn’t have
sufficient resistance. This will help identify the forces acting on
each of the elements.
Extension activities:
ANALYSIS OF DIFFERENT
STRUCTURE TYPES
Activities that extend students’ knowledge of the different
structure types
Answer key
Apply
39.
Look at the photo:
a)
What two types of structure are visible?
A dome structure and a triangular beam.
b)
Why do you think they used such different types
of structures in the same construction?
The domes and the arches provide the structure with
stability but not much span. Being lighter and having
more spaces between supports, the triangular beam is a
better option if traffic needs to pass underneath.
c)
What elements can you see in each one?
The domes have two main arches, and buttresses on
the ends. The beam has a double system of opposing
triangular beams, making them appear diamond-shaped.
d)
What is the name of the pieces that make the arch?
What is the name of the piece in the centre?
They are called arch stones, and the main one is the
keystone.
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TYPE STUDY
FUNCTION STUDY
Now we are going to study how a structure works and the different
elements according to the loads they have to bear.
First, we have to imagine how the loads are transferred from the
point where they apply to the ground and what stresses they bear
inside each structural element.
Analyse
40.
What do you think this bridge is used for? What
do you think is below it? Is it a foot bridge or
can vehicles cross over it?
41.
Write the names of the numbered elements in
the picture and say what material they are
made of.
42.
Copy the side elevation of the bridge in your
notebook. Show how it would deform under
the effect of the loads of its own weight and
the weight of people walking on it.
43.
Explain the types of stress that act on each
element under the effect of these loads.
44.
Draw arrows to show the direction of the loads
going to theground insideeachof theelements
of the bridge.
Type study a)
Type studyb)
45.
Could any other materials be used to make the
deck and the arch?
46.
How would you join the beam, the tension rods
and the deck? Design a joint for each one.
47.
Copy and complete the table.
Bridge elevation
Element
Shape Material
Function
Stress
Arch
Parabola
Holdup the
bridge
Compression
Suspenders
Deckpanels
Stretched
rectangular
prisms
Column
Steel
Brace
To reduce the
span
Plinths
Rectangular
prism
Lowerbeam
Bracing
Steel
Prevent
deformationon
the sidesof the
arch
In this study we will decide which structure has
been used in a particular construction and what
elements we can recognise in it. Now look at the
structures in these photos:
a)
In the first picture, we can see two different
structures that have been used to go across a valley
or over a hill.
❚
At the bottom of the photo there is an old
bridge, made of bricks and stone. Apart from
the semicircular arch, this is a
solid structure
. To
build these structures they use bricks and stone
walls on the outside and they are filled with other
material on the inside. Here, the arch is to allow
water to pass through.
❚
At the top of the photo there is a modern viaduct
built with
prefabricated concrete columns
and
metal triangular beams
. The triangular beams
make the structure lighter and save them from
building wider spans. This reduces the number of
columns and supports needed. They are common
in very high bridges and using a lot of columns
makes the project more expensive.
b)
This study is of the photo below. Again, we can see
two types of structures.
❚
Intheforeground,there isa
suspendedstructure
where we can see vertical metal structures, two
tension rods
and a stretched canvas as a cover.
The tension cables and canvas resist traction
stress and the columns resist compression stress,
just like in suspension bridges.
❚
In the background, we can see a
laminated
structure
, made of eight curved laminates in the
shape of a parabola. This type of curve makes
the laminates stronger so that they can support
theirownweight,even though theyare very thin.
These structures bear compression stress.
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ANALYSIS OF STRUCTURES
Apply
39.
Look at the photo.
a)
What types of structures can you see?
b)
Why do you think they used such different types of
structure in the same construction?
c)
What elements can you see in each one?
d)
What is the name of the pieces that make the arch?
And the name of the piece in the centre?
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5. Structures
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