Nature and Man Made Structures. Basic Structural Principles. Basic Structural Systems. Materials and Structures.

Frame Structures Evaluation.

3- Structures.Structures are either frame structures or shell structures, or a mixture of the two. Man-made structures follow the same principles as natural structures.

Anselm Pagès Muñoz

A lot of frame structures use triangles to achieve their strength. A rectangular structure increases its strength by adding diagonal members named trusses.

Shell structures rely on the shape. Corrugated roofing sheets, egg shells or egg boxes are made from thin, sometimes flexible materials and yet they are surprisingly strong. It is the folds and curves that make this structure strong. Ex. Try to break an egg while pressing it in one of your hands and you will realise how difficult it is. In similar terms we can see that a hollow stem supports its load as in the case of a metal tube supporting a TV aerial.

Nature and Man Made Structures. Man structures are either frame structures, shell structures or a mixture of the two. They are all based on structures found in nature. Spider webs and leaves are examples of frame structures that men apply in objects such as an umbrella.

LEAF UMBRELLASPIDER’S WEB

TRUSSES

EGG BOX

TV AERIALFind the correct words that correspond to these pictures.

Basic Structural Principles:

All structures have to stand static and dynamic loads or forces.

- Compression tends to crush or squash the structure.- Tension pulls it apart or stretches it.- Bending is a combination of compression and tension.- Torsion acts to twist a structure.

Basic Structural Principles:

All structures have to stand static and dynamic loads or forces.

- Compression tends to crush or squash the structure.- Tension pulls it apart or stretches it.- Bending is a combination of compression and tension.- Torsion acts to twist a structure.

weight

weight

Any structure develops tension, compression or both at the same time.

Bending

Weight or load on the beamT T

C C

C

T

Beams are bent by the loads on the floors, and the columns are compressed by the beams. Each material responds differently to these actions.

Steel, timber, bamboo, Iron and steel respond better at tension.

Stone, brick, adobe and concrete are strong at handling compression.

column

Which of these materials are good at responding to compression and tension forces?

Stone

Adobe

Brick

Timber

Concrete

Steel

Aluminium

Plastic

Glass

Compression Tension

Which of these materials are good at responding to compression and tension forces?

Stone

Adobe

Brick

Timber

Concrete

Steel

Aluminium

Plastic

Compression Tension

Basic Structural Systems. Trabeated System.

balcony

cantilever

lintel

Roman ruins in Ostia,

beam

post

Flying buttresses

Pointed arches

Gothic Vault.

pierButtress

Round arch and vault.

Arcaded Systems.

Roman and Romanesque

Vault

ButtressDome

Round vaultpier

pier

Simple and Difficult Arches.

Key stone

Aqueduct of Segovia www-personal.umich.edu…

Round arches from the Roman aqueducts to the

nineteenth century railway bridges.

Train bridge. Scotland

Triangular, Cable and Membrane Systems.

Triangular systems.

Cable systems.

Membrane systems.

By olimpiccable

Triangular System.

It is one of the oldest and most common ways to support a roof.

Tension member

rafters

And it can also have excellent results to build a bridge.

Tension member

Compression member

truss

The Forth Bridge and the Eiffel Tower were among the first constructions to be built with iron and using the triangular system. They were built in the highlight of the industrial revolution and soon became symbols of an era in which iron was being used for the first time in construction. The Forth Bridge is a cantilever bridge, each part is balanced on a support in the river

Both structures have a very efficient way of using stiffening trusses. Iron’s strength in both tension and compression ensure its use in different qualities and forms up to the present day.

Activity: Bring pictures of a constructionwith an iron structure. Show its stiffeningtrusses.

Ropes and Cables. Some of the largest structures in the world are made with materials strong in tension.

This is a suspension bridge. A pair of long steel cables anchored at the end and fixed to high towers suspends the roadway.

thrust thrust

span

thrust thrust

span

Forth Bridge, Scotland

The horizontal pull, named thrust, makes the towers carry the vertical weight. The taller the towers are the smaller the thrust that is needed.

thrust thrustCatenary arch

Once the cables support the

passageway, the whole structure needs

to be stabilized; this will be done by

adding a certain number of hangers,

and by giving rigidity to the passageway

with stiffening trusses. These will reduce

the torsion and bending forces that act

on the bridge. The correct location of the

towers is as essential as the correct

anchorage of the cables.

This is a structure that combines tension

(the cables), compression (the towers),

bending and torsion (the trusses).

hangers

Passageway

trusses

Membrane Systems. The shape given to thin materials can be used to form structures that

are capable of carrying loads. Bending and giving a curvature to these

materials is the way of obtaining these strong structures.

Structures with an efficient shape can reduce the amount of material required.

Cathedral of Saint Francisco.

Ex.. Folding a single sheet of paper can produce a rigid structure which will be strong enough to support a load.

Structures. Put Them in Pairs.

By olimpiccable

D

D

By olimpiccable

domecable

Name the Structural Systems as They Appear.

arcaded

trabeated

membrane

triangular

MATERIALS Tent B

BRICK

STONE

CONCRETE

IRON

WOOD

GLASS

ALUMINIUM

PLASTIC

CLOTH

STEEL

Other

Look carefully at the materials used on the outside and then at those materials used the support theinternal structure of the building. The exteriormaterials can be more like the clothes of thebuilding than part of the structure itself.

Materials and Structures. Tick thematerials you

can see.

Frame Structures.The support of a house needs acting structures that carry the loads.

Tower.

COMPRESSION FORCES OR STRESSES

Beams in between columns

TENSION FORCES OR STRESSES

LOAD AND SUPPORT

Flying buttresses.

Buttresses on the sides.

Frame Structures.

To make a structure strong, designers have to try and calculate theforces that will act on it. What are the forces in these two constructions?Look at the building and distinguish the dynamic forces from the static ones.

Forces that Materials and Structures Have to Support.

2- Lateral movements.

1- Vertical movement loads.

3- The settling movements of the building.

4- Earth movements.2- Lateral

movements.

1- Vertical movement loads.

Forces that Materials and Structures Have to Support.

5- Furniture’s weight.

6- People’s weight, movements, music, noises and vibration.

1- Vertical movement loads.

2- Lateral movements.

3- The settling movements of the building.

4- Earth movements.

Forces that Materials and Structures Have to Support.

7- Temperature changes

8- Rain and humidity. 9- Snow’s weight.

10-Wind pressure.

5- Furniture’s weight.

6- People’s weight, movements, music, noises and vibration.

1- Vertical movement loads.

2- Lateral movements.

3- The settling movements of the building.

4- Earth movements.

Forces that Materials and Structures Have to Support.

Requirements of a Building.

4- Solid roof with thermal insulation and waterproof materials; tiles or slates, paint, etc.

3- Materials and structures that tolerate expansion and contraction at different temperatures.

5- Façades with thermal insulation and waterproof materials.

6- Thermal and noise insulated floors and walls

1- Solid foundations

2- A solid structure made of steel or reinforced concrete.

Evaluation: Describe a Structure or a Building. Name the parts, the materials used and explain their functions. Prepare a power point presentation.

Pier

It is 330metres long and 4 metres wide It was built by Norman Forster and partners. It is a suspension footbridge constructed with two Y reinforced concrete frames and eight cables.

Deck

South abutment

Cables

Northern support and

cable anchorage

Hand railing

South cable anchorage

South cable anchorage

Stabilizing beam

Millennium Bridge. London 1996-2002

Cables are tensed

Piers are compressed

Vertical and lateral movements.

Torsion is avoided