Compression

On the 7th of March 2014, the first studio class in Constructing

Environments focused on ‘compression’. In order to gain great knowledge

of compression within building structures, we first must understand the

two loads, static and dynamic. Static loads are loads that are applied to

a structure slowly or permanently as oppose to dynamic loads which are

applied very rapidly and unexpectedly like wind loads and earthquake.

Initially, when we were building the tower, there were only static loads,

or dead loads, which were the blocks we used to build the tower. As the

blocks are stacked on top of one another, a compression force is

produced as the “particles of the material compact together” (Newton,

2014). When we had to make space for a toy dog to fit inside our tower,

we compressed the blocks on top of each other from the two sides of the

entrance and slowly built it closer to each other as the construction rose.

As we can observe from ‘Tower 1’, the load path from the two blocks on

top of the entrance will travel from the middle to the outer sides and then

down the blocks and to the sides until it reaches the floor. When it

reaches the floor, there will be a reaction force from the ground up in

order to keep the structure stable. Keep in mind that when the load path

travels down to the ground, it takes the most closest or direct path from

one block to another.

With a solid foundation, and too much material being used, the group tried to be more efficient and put gaps in our tower

about halfway to the highest point. Same with the bottom half of the structure, the load forces will just travel to the sides and

down the most direct route given to them. But by having gaps, the structure won’t be as compacted as its foundation and this

may not be optimal for a strong building as a dynamic load, the wind, will enter the load more easily. So as the tower

progresses, it is noticeable that the tower is starting to deform and become weaker. This is due to the dynamic wind load

travelling in a horizontal direction to a tower, which its load force travels downwards. Another thing that we learnt in the week

one studio class was the structural forces.

As class time was almost up, the class watched a few groups deconstruct their tower. From

our view, it was seen that the tower will hold its deforming structure until about 10% of its

load from around the

bottom before

collapsing. This is

possibly due to the

instability of the

forces. The loading

forces of the structure

must have not be in

equilibrium with its

reaction force in

addition to the

dynamic wind force

causing the demolition

of the tower.

In accordance to the sketch, it is evident that the tower’s

force is collinear. It is collinear as the forces occur along a

straight line.

Ching, F D.K. (2008). Building Construction Illustrated. 4th ed. New Jersey: John Wiley & Sons. p2.08-2.11.

Newton, C. (2014). ENVS1003: Constructing Environments Basic Structural Forces (I). Retrieved from

https://app.lms.unimelb.edu.au/bbcswebdav/courses/ENVS10003_2014_SM1/WEEK%2001/Basic%20Structural%20Forces%201.pdf

Structural Joint

Balsawood Tower

During the studio session, we were to build a tall tower but except this time made out of

balsawood. The aim of this tower was to maximise its height by using a suitable frame without making

the tower fall down. My group initially decided to build the tower in a square shaped figure like buildings

in the streets. We came to figure out that the objection of this task was to build a tall tower rather

than a strong structure that would withhold objects. Thus with the limited amount of supplies we were

given, we changed to a triangular shape, knowing that it’d be more efficient and more effective if done

properly. As demonstrated in ‘Balsawood 1’, we connected strips of balsawood via a locking system

with masking tape around it for reinforcement. By doing this, we assume that the load force will be

more compacted hence become stronger than loose joints.

In ‘Balsawood 2’ is our final form of the balsawood tower. We first structured it by creating a base at

the bottom so that the load force can equally travel down for a stable structure. We sticked the woods in

line with the locking frame as well as taping it around. In order for the structure to stay up, we thought

about adding a strip of wood at the bottom to connect with the long frame that we were going to stick

for height. By connecting on a supporting stick, I assume that the loading force of the structure will be able to withstand more force thus

causing deformation to happen a little later than expected.

Locking

system

In ‘Balsawood 3’, we examined a great structure by another group. They criss-crossed the middle of their structure as well as had a

strong hold at every edge of their exterior sticks. By doing this, they have created a strong tower as the forces travel down more equally

and most of all, creates a

frame that is very stable.

The

supporting

frame.

Week 3- Footings & Foundations

Structural Elements

Geometry & Equilibrium

Footings & Foundations

The foundations main function “is to safety

transfer all loads acting on the building

structure to the ground.” It must also resist

against the soil pressing against the

foundation wall.

Whenever you see a cracking in a building, it

is due to the ‘settlement’ being uneven.

Hence why footings and foundation are

designed to overcome this problem and

hopefully keep a structural building fixed and

stable. They also should be able to support he

‘bearing capacity’ of the soil.

Shallow footings are used when soil

conditions are stable and their bearing

capacity is closed to the ground, transferring

vertically from the foundation to the ground.

Deep foundations are used when soil

conditions are unstable and their bearing

capacity is far from the top of the ground.

Load is transferred from the foundation to the

unfitting soil and into the deep level where

elements like bed rocks and gravel exists.

There are two types of piles for the

foundation which are end bearing piles and

friction piles.

Mass and Masonry Materials

Mass materials are: stone, earth, clay,

concrete. They are strong in compression but

weak in tension. They are hard, good thermal

masses and durable.

Masonry is made up of stone, clay and

concrete.

Glossary

Settlement: As time passes, buildings

compress into the earth’s ground thus sink a

bit into the earth.

Foundation (retaining) wall: Used on sites

creating a basement for stability. Pressure

load behind the wall needs to be considered

to prevent wall from collapsing.

Centre of mass- “The point at which an object

is balanced.”

Equilibrium- It is the state of rest where an

applied force is equated to its reaction force.

(I.e. a support element has to react equally

and in the opposite direction to a load).

Moment of force- “The tendency to make an

object or a point rotate.”

Masonry definitions:

Bond- “the pattern or arrangement of units”

Course- “A horizontal row of masonry units”

Mortar- “mixture of cement or lime, sand and

water used as a bonding agent”.

Week 4- Floor Systems & Horizontal

Elements

Beams and Cantilevers

Span & Spacing

When dealing with span and spacing, we just need

to remember that “spacing of the supporting

elements depend on the spanning capabilities of

the supported elements”

Floor & framing Systems

There are three types of flooring system that

we briefly learnt in class. First one was

concrete flooring then timber flooring and

finally steel flooring.

Concrete flooring has two types of spanning.

They have a two way span as well as the

typical one way span which spans between

two of the shorter supporting structures. Two

way system is ideal for square bays and one

way system is more efficient when structural

openings are rectangular. The system

depends on floor load, cost efficiency and

even function of building like distance

between columns for carparking.

Steel framing takes many forms, with some

using ‘heavy gauge structural steel members’

but most using ‘light gauge steel framing’.

They sometimes combine with each other or

concrete slab systems. Spanning of the

materials determine spacing of the supports.

Timber floor framing systems uses “a

combination of bearers (primary beams) and

joists (secondary beams).” Span of bearers

determines spacing of piers/stumps and their

spacing equates.

Concrete (Artificial stone)

1 part cement (Portland/lime): 2 parts fine

aggregate (sand): 4 parts coarse aggregate

(crushed rocks): 0.4-0.5 part water.

A chemical reaction, hydration, takes place

when cement and water are mixed, leading to

the release of heat. Crystals are formed

during process, joining the elements of

concrete together. If too much water is

added, final concrete will be weaker. If too

little water is added, the concrete will be too

stiff and hard to work with. Thus an

advantage of concrete is that it is fluid and

shapeless before hardening, making it easy to

work within terms of shaping it.

Concrete needs formwork because when wet,

it is very heavy. It can be achieved via ‘props’

and ‘bracings’. Keep in mind that concrete

reaches about 75% of its compressive

strength in about 7 days, with testing for

required strength on the 28th day. Also,

formwork can be built in situ (on site) or pre-

cast (in factory beforehand). When concrete

is hardened and strong enough, the formwork

is usually removed, stored and reused

otherwise may stay in place forever

(sacrificial formwork).

Concrete is strong in compression and weak

in tension thus steel or mesh, strong in

tension, is added for reinforcement. This

results in reinforced concrete.

The properties in concrete are that it is high

in hardness (can be scratched with metallic

object), medium to high in density (2.5

denser than water), medium to low in

porosity (absorb fluids), permeability

(allowing gas/liquid to pass through) and

reusability/recyclability, low in fragility

(chipped with hammer) and

flexibility/plasticity and very low in ductility.

It is also a poor heat and electric conductor,

typically very durable and long lasting, non-

renewable and cost effective.

Since it is permeable, it is not completely

waterproof thus if steel bars are too close to

surface, they will not be protected from

moisture and oxidation resulting the structure

to be degraded. Another problem with

concrete is ‘poor vibration of the concrete’

which makes it hard to get rid of air bubbles

during the pouring process and thus may lead

the element to failing.

Glossary

Beam- horizontal structure that carries loads

along its length and transfer the loads to the

closest vertical supports.

Cantilevers- an overhanging portion of a

structure that transfer loads to the support.

Span- “Distance measured between two

structural supports”

Spacing- The repetitive distance between

chains of elements. Measured from centre-

line of one element to the next one.

Girders- main beams

Joists- secondary beams

Formwork- temporary support/moulds used

to hold liquid concrete in place until it

hardens.

Week 5 – Columns, Grids & Wall Systems

Columns, Frames & Grids

Columns are vertical structural members designed

to transfer compressive loads. Short columns have

shorter length and thicker cross-section and long

columns are the opposite. Columns are considered

short if column length to the smallest cross section

is 12:1 otherwise it’s a long column. Short

columns fail by ‘crushing’ and this happens when a

compressive load exceeds the compressive

strength of the column. Long columns fail by

‘buckling’ and the buckling is determined by the

length of the long column as well as how fixed the

top and bottom of the column is.

Both a ‘fixed’ and ‘hinged’ frame is a rigid frame

but a fixed frame is connected to its supports with

fixed joints and a hinged is connected with pin

joints. The third frame is a ‘three-hinged’ frame

which is two firm frames connected to each other

and its support with pin joints.

Walls, Grids & Columns

There are three types of wall systems, being the

structural frames, load bearing walls and stud

walls.

The frames can either be of concrete material,

steel or timber which is rarely used here. Load

bearing wall is made of either concrete or

masonry. Stud walls will either have light gauge

steel framing or timber framing.

As of the grids, concrete frames “use a grid of

columns with concrete beams connecting the

columns together.” Steel frames “use a grid of

steel columns connected to steel girders and

beams.” Timber frames use “a grid of timber posts

or poles connected to timber beams.” They require

bracing on the corners to stabilise the structure.

Load bearing walls come in three materials. First

off is ‘concrete’ which the wall can be completed in

situ or pre-casted. They are used in nowadays new

apartments. Next is ‘reinforced masonry’ blocks

which can be strengthen via a reinforcement steel

rod or some other material being placed through

its core. Solid masonry can be formed via single

concrete or clay bricks. It can also be formed with

multiple bricks, joint using a brick turned ninety

degrees or wall ties placed within the mortar bed.

When using two skins of masonry, you may be

constructing cavity masonry walls where two walls

are built beside each other with a gap between for

better thermal performance, waterproofing,

insulation and running services within the wall

cavity. This opening can be pointed out when

damp proof course or weep holes are presented in

the masonry walls.

Stud framing

Timber

The properties in timber are that it is

high in flexibility, porosity/permeability

and reusability/recyclability, medium in

plasticity (easy to shape), medium-low in

hardness and fragility and low in ductility.

They are poor heat and electric

conductors and their density extremely

varies depending on the type of timber.

It is normally cost effective

A weak point in timber is a knot which

causes a slope in the grain thus breaks

easily. You should also be aware to

protect the end of the material from

water whether is it by painting or even

detailing. Timber can also be damaged by

insects, sunlight and heat, fire and

chemical exposure.

Glossary

Nogging- A row of an element (timber/steel)

in stud walls between the top and bottom

plates, placed to prevent buckling of long thin

members.

Buckling- Bending of a member due to heavy

load. Normally happens with long columns.

Porosity- Ability to absorb fluid

Permeability- Ability to allow fluids

(gas/liquid) to pass through

Wall ties- a metal piece connecting a masonry

wall to another wall.

Week 6- Spanning & Enclosing Space

Trusses, Plates & Grids

Trusses require bracings that are perpendicular to

their planes. Their increased depth allows them to

span greater than steel beams and girders. They

also allow mechanical services such as pipping or

ductwork to pass through the web spaces.

Plates are fixed structures that spread out applied

loads in a multidirectional pattern to the closest

support. It should be ensured that the plates are

nearly square or square so that it behaves as a

two-way structure thus spreading the load equally

all around.

Folded plate structures are thin elements that form

sharp angles to brace each other against

‘buckling’. Each plane behaves as a beam in the

long direction.

In trusses, the grids are normally the steel beams

and girders structured in a triangular shape while

in plates, there are none unless beams are used to

support under them.

Roofing Strategies and Systems

There are two types of roof systems, the flat

roof and the sloping roof. The flat roof can be

made of concrete slabs, flat trusses, beams

and decking or joists and decking. The

sloping roof is made of rafters, beams or

purlins or trusses.

Concrete roofs are generally flat roofs and

they slope towards drainage points. They are

finished with waterproof membrane.

Space frames are 3D plate structures

that are long spanning in two directions.

They look like matrix structures with the

crosses.

Metals

Metals are malleable and ductile but not

brittle. Their hardness varies depending on

the type. They are low in fragility and can be

medium-high in flexibility when melted. It is

generally impermeable and is high in density.

Metal is also a very good heat and electric

conductor. They can normally last long and

even be reused thus making them quite cost

effective.

Metals will directly transfer ions if in contact

with another metal. This may cause corrosion

and we can reduce this effect with insulators

like rubber gasket. Taking this into

consideration, we should consider keeping

water away from metal as much as possible

to reduce oxidation and corrosion which will

cause the metal to rust. We can do this by

avoiding moisture, sealing the metal against

moisture, or give the metal a chemical

treatment.

Glossary

Truss- A structure consisting of triangle

members with forces acting in either

compression or tension.

Web- System of members connecting the top

and bottom chord of a truss together.

Ferrous- Iron

Non-Ferrous- All other metals. More

expensive but less common.

Alloys- Combination of two or more metals.

Week 8- Openings

Deformation & Geometry

The efficiency of a beam can be improved

by configuring the cross section. This

provides the required ‘moment of inertia’

or ‘section modulus’ with the smallest

possible area. The moment of inertia is a

geometric property, indicating how the

cross sectional area of a structural

member is spread out and does not

reflect the physical properties of a

material. Section modulus is also a

geometric property.

Strategies for openings

Sill allows water to run away or drip rather

than run in the door itself.

You normally work off manufacturer frames

because too much time and money to set up

for own design.

Windows needing to be clean is an issue thus

why skyscrapers have facades.

Curtin walls act both a window and wall

because it is a see through wall. Quite ideal

for office rooms.

Glass

Glass is made from formers. They are non-

porous and waterproof. They have a medium

to high density and can transmit heat and

light but not electricity. Glass is also high in

hardness, fragility, reusability, durability,

flexibility and plasticity when molten but low

in ductility. They are quite expensive to

produce and transport.

There are two main types of glass, flat glass

and shaped glass but float glass is the most

common one nowadays. Clear float glass is

the simplest and cheapest glass, ideal in low

cost purchase. Laminated glass is much

stronger and can still crack but the cracked

fragments tend to stick to the plastic rather

than falling apart. Tempered glass is

produced by heating. They are 4 to 5 times

stronger than annealed glass. When cooled,

they create a compression force outside the

surface of the glass. They are perfect for

highly exposed situations or when a large size

is required.

Glossary

Fluxes- help formers to melt at low

temperatures.

Stabilizers- combine with formers and fluxes

to keep glass from dissolving or crumbling

Neutral axis- An imaginary line passing

through the middle of the cross section of a

beam.

Shearing- part of a structure break off due to

compression or tension force.

Moment of inertia- “The sum of the products

of each element of an area and the square of

its distance from a coplanar axis of rotation.”

Section modulus- The moment of inertia of

the section divided by the distance from the

neutral axis to the most remote surface.”

Axial load- Forces acting along the line of an

axis of a material.

Week 9- Detailing Strategies 2

Stress and Structural Members

Columns are rigid structural members

designed to support ‘axial compressive loads’

applied to the ends of the structure. Thick

columns fail by crushing rather than buckling

and this occurs when the stress from the

axial load exceeds the compressive strength

of the material in the cross section. However,

an unusual load can cause the member to

bend due to imbalance. On another note, long

columns firstly deflect before failing by

buckling. If you can reduce the slenderness,

it will cause the column to less likely buckle.

Construction Detailing

Health and safety is an important detailing.

Such as requiring rails for stairs.

Materials must be chosen carefully as this can

save structure in long time, making them

more durable. For example, using copper will

improve its appearance overtime unlike

timber which greys and becomes damaged

overtime.

Another detailing matter is surfaces, and how

easily they can be repaired such as skirtings

which will prevent damage from vacuum

cleaners or foots walking into it.

Cleanable surfaces are another detailing

problem. Restaurants and hospitals need to

have easy clean surfaces. Materials must be

chosen carefully along with detailing.

Constructability is another matter. It should

be easy to assemble, easy to adjust due to a

mistake and efficient with materials and

labour. This is why it is best to use structures

that are already designed or detailed to suit

the construction rather than create a new one

which will be very pricy.

Composite Materials

“Composite formed from:

1. Combination of materials which differ

in composition or form

2. Remain bonded together

3. Retain their identities and properties

4. Act together to provide improved

specific or synergistic characteristics

not obtainable by any of the original

components acting alone.”

Composite materials can come in fibrous,

laminar, particulate or hybrid.

Glossary

Kern area- The central area of an horizontal

section of a column or wall which all

compressive loads must pass if presented.

Slenderness ratio of a column- It is the ratio

of “its effective length to is least radius

gyration”.

Effective length- “The distance between

inflection points in a column subject to

buckling.”

Effective length factor- “A coefficient for

modifying the actual length of a column

according to its end conditions in order to

determine its effective length.”

Radius of gyration- “The distance from an

axis at which the mass of a body may be

assumed to be concentrated.”

Week 10- When Things Go Wrong

Lateral Forces

Resistance to lateral loads are a major

concern to designing buildings. Such forces

can be of earthquake or wind. The structures

must be resistant to these forces in both the

horizontal and vertical direction.

Diaphragms collect forces in the horizontal

direction and transfer these forces into the

vertical bearing elements. An example of a

diaphragm is reinforced concrete.

Brace frames are essentially truss structures

that move loads diagonally through the

structure in a vertical plane.

Shear walls resist lateral loads in the vertical

plane. They collect loads from the horizontal

elements and transfer them to the

foundation.

Moment resisting frames are structural

elements connected with fixed joints. Hence

why they are resisted by the rotation and

bending of the beam and column joints.

Seismic bas isolators are connections placed

between the foundation and the substructure.

This allows superstructure and substructures

to move independently if there is an

earthquake.

Collapses & Failures

Material selection

Exposure to hot sun

Painted black on outside only

Fasteners

When looking at material selection, should

consider:

Exposure

Compatibility

Strength and deflection

Long term performance

Maintenance

Construction & detailing

Heroes & Culprits

When choosing materials, consider:

health

waste/recycling/recycled

energy used and embodied energy

pollution

life cycle

Construction Workshop

Structural Performance

We decided to place the longest length of the

pinewood on top of the other one and stick

two plywoods on each side of the woods as

demonstrated in the picture below. We did

this with thought that the plywood wills

strongly withstand the machine as long as the

machine is crushing it from the top and

bottom, where its strongest point is at and

not the wide where it can bend and deviate a

lot. We did not worry about the pinewood too

much as there was no weak spots (knots)

and it looked very dense compare to the

plywoods.

Failure Mechanisms

Our structure failed because the plywood

failed to stand balanced and started to bend

(can be seen in the picture top far right)

which caused it to snap as there was too

much tension for the wood to manage. This

also led the pine wood to break as nails failed

to hold the woods together.

Materials & Tools Used

My team was given two hard plywoods and

two rectangular pinewoods.

We used a saw to even out the structure but

mostly used a hammer and nails to fix the

woods together.

Record of our structure

Our structure’s applied failure load

was about 360kg before snapping to

one side.

It had a maximum deflection of

43mm, starting at 162mm and ending

at 205mm.

Span, Shape, Strength, material

efficiency and joint types

Our construction spanned 1050mm

rather than the recommended

1000mm in case of structural failure.

It was shaped typically like a

rectangular block without gaps for

strong resistance.

Pinewood is very material efficient as

it is cheap and easily machined.

Plywood is also cheap but if

structured incorrectly, the wood’s

strength will not be maximised but

very weak.

We only used fixed joints, nailing

mostly at the top due to compression

and less at the bottom since in

tension.

Comparison to the strongest structure

Unlike another team’s structure, seen above, they

had 3 square-dimensioned like pine wood attached

on top of each other which ultimately withstood

the machine the strongest. Their structure was

crushed due to the knot, known as a weak point,

in the middle which can be seen. This was a

material failure and not their construction in the

structure thus it could have held much more load

then observed. Their applied failure load was about

460kg and deflected 60mm.

Comparison between actual construction

materials & scale model making materials

Plywoods are normally stuck together thus

why it is strong unlike our model materials

where we only used a single layer which also

made shaping it hard.

Nothing was different with the pinewoods.

References

Ching, F D.K. (2008). Building

Construction Illustrated. 4th ed. New

Jersey: John Wiley & Sons.