structure and construction materials

8/12/2019 Structure and Construction Materials

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Intro to Structures

Lecture 1Intro to StructuresBuilding Construction and Technology 2


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Intro to Structures

Structures in Nature

Manmade Structures

Industrialized Structures



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Structures in Nature

Natural structures can be divided into

three categories:-

Structure in Plants

Structure of Animals

Structures that Animals Build



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If you look closely at a leaf you can see how the main rib tapers from

the base, the point where the whole weight of the leaf is borne from.The other ribs spring from the centre rib in a regular pattern and taper

from the centre to the edge. The whole leaf can be looked at as the

way nature has evolved a mechanically sound structure that elegantly

performs its desired functions in the conditions in which it grows. A

leaf is a perfect example of a lightweight structure in nature.

Structure in Plants



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If you look closely at the head of the

sunflower you will see that the seeds are

arranged so that a pattern is formed by

spirals winding out from the centre.

If you examine the head in greater detail

you will notice double spiraling. This is

where two opposite sets of rotating spirals

are formed by the arrangement of the

individual florets in the head of the flower.



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Structure of Animals.The image opposite illustrates the structure of an insects eye, which is

composed of many parts and all these parts have to be held together

and supported. This is done by a geodesic dome grid on the outside

surface of the eye which by its nature takes the shape of a hemisphere.

The whole structural framework of the domed grid is held firmly in

position and this in turn provides a stiff and strong support for the

cornea. This enables the insects eye to function efficiently. The concept

behind the geodesic domes which Buckminster Fuller designed are the

very same as the structure of an insects eye.



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The body structure of animals is a system of balancedbeams and masses. Animals bodies therefore must be

balanced otherwise they would fall over due to the pull of

gravity.



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Structures that Animals BuildInsects and animals play a more active role in thebuilding of their homes. The web of the spider, the dam

or lodge of a beaver or the structure of the termite are

designed in such a manner so as to support the

creatures activities.



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Magnetic Termite Mound in Australia

These termite mounds in Australia are aligned north-to-south as

a means of temperature control.



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Spider web


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The spiders web is one of the

most fascinating and interesting of

structures constructed by animals.Although it may appear at a

glance to be randomly

constructed it follows a basic

pattern.



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Spiders webs have been proven to be so resilientthat in tests the web of the Nephila spider wascapable of repelling a moving bullet.



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By examining structures in nature we can

see where the principle exists and see

how these principles are incorporated in

structures today.



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Manmade Structures



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Structures have developed gradually over time but

there were two main factors that affected thedevelopment of structures:-

The availability of tools for cutting and shaping.

During the stone age stone axes and flints were used to cut the wood

but due to the nature of the tools methods of jointing were limited.

With the advent of the Bronze and the Iron Age new materials were

available and therefore improved tools.

Methods of construction and building techniques.

As peoples needs changed so to did their building techniques. With the

improvement in the different types of tools that were available they

was also a development in the methods of construction, such as

improved jointing techniques.



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As these two factors changed over time,

so to did the type of structure that were

being constructed. We will take the

example of timber and trace its

development in the use of construction.



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Early structures such as this circular hut wereconstructed form branches and stakes and they

were jointed at the apex using strips of bark. No

tool were required in the construction of such a

hut.



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With the development of tools such asstone flints, basic jointing started to occur.

It evolved from being tied as above to the

use of natural forks and finally basic

shaping and jointing.



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Frames started to change shape and

developments started to occur not only in

the jointing but also in the foundations.



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Structural members started to become more

square in section and more elaborate

jointing such as halving and mortise and

tenon joints were developed.



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Colosseum


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One thing we have to keep in mind when comparing natural and manmade

structures is that nature uses live materials while man uses passive ones andthe two do not always behave in the same manner.


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Industrialized Structures



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Northern Pacific Railroad Bridge, 1872



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Construction and Materials


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Construction and Materials

Major Types of Materials for Building

Construction

Criteria for Selecting and Using a Building

Material

Lecture 2 Construction and MaterialsBuilding Construction and Technology 2

Major Types of Materials for


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Major Types of Materials for

Building ConstructionEarth Plants Metal Composite

Raw Materials Mud

Stone

Lime

Trees/Woods

Straw

IndustrialMaterials

BrickCement

Block

Glass

LumberBoard

Laminated

Wood

Plywood

Board

IronSteel

Aluminium

ReinforcedConcrete

Fabric

Structures

Membrane


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Timber



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B d


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Boards



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St l


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Steel



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St


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Stones



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http://www.hubbardston.org/Photographs/Town2003/05%20Matherton%20Stone%20House.JPGhttp://www.hubbardston.org/Photographs/Town2003/05%20Matherton%20Stone%20House.JPG


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Bricks


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Bricks



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Concrete


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Concrete



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Lecture 2 Construction and Materials

Building Construction and Technology 2


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Criteria for Selecting and Using aBuilding Material


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Building Material

Material for Structural Purposes Elasticity and Stiffness

Dimensional Stability

Material for Partitioning or Finishing

Water Resistance Thermal Conductivity

Transmission, Reflection or Absorption

Density

Combustion

Design Scheme

Standard Shapes and Sizes



Material for structural purposes


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Material for structural purposes

Each Material has different properties ofstrength, elasticity, and stiffness. The most

effective structural materials are those that

combine elasticity with stiffness.



Elasticity


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Elasticity

Elasticity is the ability of amaterial to deform under

stress bend, stretch or

compress and return to

its original shape whenthe applied stress is

removed. Every material

has its elastic limit

beyond which it will

permanently deform orbreak.



Termed Ductile


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Termed Ductile

Materials thatundergo plastic

deformation before

actually breaking are

termed ductile.



Brittle materials


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Brittle materials

Brittle materials, on theother hand, have low

elastic limits and rupture

under loads with little

visible deformation.Because brittle materials

have less reserve

strength that ductile

materials, the are not as

suitable for structuralpurposes.



Stiffness


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Stiffness

Stiffness is a measure of the forcerequired to push or pull a material to its

elastic limit. A materials stiffness, along

with the stiffness of its cross-sectionalshape, are important factors when

considering the relationship between span

and deflection under loading.





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The dimensionalstability of a material as

it responds to changes

in temperature andmoisture content affects

the manner in which it

is detailed andconstructed to join with

other materials.



Water Resistance


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Water Resistance

The resistance of a material to water andwater vapor is an important consideration

when it is exposed to weather or used in

moist environments.



Thermal Conductivity


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Thermal Conductivity

The thermal conductivity or resistance of amaterial must be assessed when it is used

in constructing the exterior envelope of a

building.



Transmission, Reflection or

Ab i


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Absorption

A materials transmission, reflection, orabsorption of visible light and radiant heat

should be evaluated when the material is

used to finish the surfaces of a room.



Density


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Density

The density or hardness ofa material determines its

resistance to wear and

abrasion, its durability inuse, and the costs

required to maintain it.



Combustion


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Combustion

The ability of a material to resistcombustion, withstand exposure to fire,

and not produce smoke and toxic gases,

must be evaluated before using it as astructural member or an interior finish.




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Many building materials are manufacturedin standard shapes and sizes, These stock

dimensions, however, may vary slightly

from one manufacture to the next. Theyshould be verified in the planning and

design phases of a building so that

unnecessary cutting or wasting of material

can be minimized during construction.



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