5
Structures
118
6.4.
Buttresses and flying buttresses
These elements support the loads of arches and vaults and transfer
them to the foundations. Flying buttresses are curved elements
that transfer loads from the arch to the buttress. A buttress is a
vertical element which may or may not be attached to a wall. The
main function of a buttress is to reinforce the wall and carry the
loads from the vaults to the ground.
6.5.
Load-bearing walls and retaining walls
These are vertical elements that transfer the load to the ground.
The difference between them is that load-bearing walls bear
compression forces while retaining walls resist bending forces.
Stone and brick are used in the first type of wall, while reinforced
concrete is used in the second. Currently, concrete is the type of
material most commonly found in both types.
6.6.
Concrete slabs
These are horizontal elements that resist bending forces and
transfer the load to the rest of the structure. Slabs are often made
up of joists, blocks and a top layer of reinforced concrete. Each
one has a specific function: the joists carry the weight of the slabs
to the beams, the blocks cover the spaces between the joists and
the top layer provides a uniform surface and ensures that the
loads are spread uniformly. The blocks over the spaces are not
strong, despite their appearance, and it is therefore important not
to put any weight on them when working on site, in case they
give way.
In the margin there is a photo showing the hardened concrete
mould. This is a fundamental aspect of constructing with concrete,
and it enables students to see the shape of the different structural
elements.
6.7.
Footings, plinths, shallow foundations
and piles
Essentially, these are the four main types of foundation. The
decision to choose one over another depends on the type of
building and on the characteristics of the ground. All share the
same function of transferring loads from the structure to the
ground underneath.
6.8.
Suspenders and tension rods
The most significant feature of these elements is that they are
linear and only bear traction forces. They are used mainly in
suspension structures or cross-bracing.
Reinforcement activities:
TYPES OF STRUCTURE
Activities giving further practice on different types of structures.
Answer key
Apply
37.
In the photo we can see the formwork of the main
beams of a concrete slab. Find the start rebars of the
pillar, the rears of the beams, the temporary jack posts
and the safety net.
The reinforcing bars are clearly visible in the middle of the
photo; the reinforcing bars for the beams are around the edge
and in the centre. The net runs around the edge and across
the central space and a jack post is visible below the concrete
slab.
114
115
5. Structures
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6.6.
Concrete slabs
These are horizontal elements working in
two directions. They transfer the loads that
the rest of the structure bears and they
resist bending stress. They are made up of:
❚
Joists
: carry the weight of the slabs to
the beams.
❚
Blocks
:fills the spacebetween the joists.
They are hollow elements that help to
make the slabs lighter.
❚
Reinforced concrete surface
: makes
the slabs even.
6.4.
Buttresses and flying buttresses
These are used to hold up the loads of arches and vaults.
❚
A
buttress
can be part of a wall and is used to reinforce the wall and transfer
the loads from the vaults to the ground.
❚
A
flying buttress
is an exterior arch which bears lateral loads from the vaults
to the buttresses, which is the vertical element which holds them up.
Nowadays we use reinforced concrete as well as stone.
Joists andblocks
6.7.
Footings, plinths, shallow foundations and piles
Thepurposeof theseelements is todistribute the loadof the structure,buildingor
bridgesothat itdoesnotsink.Theseelementstogetherarecalledthe
foundations
.
There are different types:
❚
A
footing
is a type of
platform
34
at the base of a structure that holds the
weight of the rest of the structure.
❚
Plinths
are rectangular blocks of concrete under columns.
❚
Shallow foundations
are made of concrete that sit on the ground and are
used to distribute loads. They are usually used for soft ground.
❚
Piles
are columns
driven
35
deep into unstable ground or
clay
36
, so that they
rest in
firmer
37
soil.
Apply
38.
In your notebook, draw diagrams of the structures on these pages.
Label the structural elements, the material used in each part of the
structure and identify the types of stress each part bears.
What stress do concrete and reinforced concrete elements usually
bear? And steel elements? Why do you think that is?
6.8.
Suspenders and tension rods
Theseare linearelements,normally steelcables,whose function is to resist traction
stress. They are used in suspended constructions and in bracing.
6.5.
Load-bearing walls and retaining walls
These are
vertical elements
that transfer loads to the ground.
❚
Load-bearing walls
bear compression stress and can be built with materials
like stone, bricks and adobe.
❚
Retaining walls
bear bending stress because of the force that the earth puts
on them. They must be built with reinforced concrete or with a large amount
of material.
Structural elements are
classified by the following
functions:
❚
Resistingcompressionstress:
pillars,columnsandpilasters.
❚
Creating a space between
horizontal elements: beams,
joists and lintels.
❚
Filling the space between
two walls or columns with a
curved element: arches and
vaults.
❚
Holding up the loads of
archesandvaults:buttresses
and flying buttresses.
❚
Transferring loads to the
ground: load-bearing walls
or retaining walls.
❚
Transferring the loads from
slabs: joists, blocks and
reinforcedconcretesurfaces.
❚
Distributing loads in the
ground: footings, plinths,
shallow foundationsandpiles.
❚
Resisting traction stress:
suspenders and bracing.
Key concepts
Apply
37.
In the photo, we can
see the formwork of
the main beams of a
concrete slab. Find the
start rebars
32
of the
pillar, the rebars of the
beams, the temporary
jack posts
33
and the
safety net.
Concreteneeds amould
31
until it
getshard (or sets).This temporary
mould is called formwork
start rebar
Flyingbuttressesandbuttresses
Buttresses
Load-bearingwall
Retainingwall
TheAlamilloBridge, Seville
Bracingonbuttresses
Foundationswith footings
Foundationswithpiles
beams
31
mould
: a frame onwhich something
is constructed
32
start rebar
: steel rebar that comes
outof apillar so that construction can
continue
33
jack post
: a steel post used in
construction
34
platform
: a raised structure which
supports another element
35
drive
:move by using force
36
clay
: earth that is made up of small
pieces, used tomake bricks
37
firm
: almost solid surface
