Engineering Studies: CIVIL STRUCTURE

Civil Structures

• All engineered structures in our world

1. BEAM BRIDGES - defintion

A member that is supported so that its supports do not carry longitudinal force, ONLY VERTICAL

Beams can be classified into 2 types:

• Simply supported beam

• Cantilvered Beam

Simply supported Beam

• Supported at both ends

Cantilvered Beam

• Supported at one end

Outline the history of technological change as applied to civil structures. (3) timbe-sto-steel

• The first civil structures were developed using materials that were readily available such as timber.

• Later bridges were constructed from stone.

• During the Industrial Revolution, steel replaced timber and stone

Who were early Beam Bridges made by…

• Romans

Truss Girder Bridges (when was it developed)

• Developed in 1500s

Box Girder Bridge

• Most common form of Beam Bridge today

• Consists of a tube with a rectangular cross-section stiffened by a series of internal walls.

2. Arch Bridges

A bridge with a curved structure that supports the load and transfers forces to the ground at each end.

Materials used on Arch Bridges

• Stone

• Cast iron and steel.

• Modern arch bridges use concrete.

Characteristics of Stone (3) + 1 disavdtage

• High compressive strength, weak in tension – withstands large squeezing forces.

• Durable – lasts a long time and resists weathering.

• Heavy – provides stability to the bridge.

Characetirics of Cast Iron (2 advantage +.1 disad

• Strong in compression, weak in tension

• Cheaper

Characteristics of Steel (3 ADV+ 1 DISA (corro..)

• High tensile strength – withstands large pulling forces.

• High compressive strength – withstands large squeezing forces.

• Ductile – can bend or deform without breaking easily.

CAN CORRODE EASILY

3. Suspension Bridge

• A bridge where the deck is supported by vertical cables suspendes between tall towers

Suspension Bridges description (made from what, more ligh.., what material used mainly)

• Early suspension bridges used twine, vine or chains

• Suspension bridges are much more lightweight so can span further distances

• Steel is commonly used in the manufacture of suspension bridges

4. Opening Bridge

Moves or lifts to let ships pass underneath.

Engineering Innovations in Civil Structure and their Effect on Peoples Lives (innovation vs invention

• Invention is the development of something new

• Innovation refers to altering something already made

Construction and Processing Materials used in Civil Structure

T,S, B, CI, WI, S, C, SS

• Timber

• Stone

• Bricks

• Cast Iron

• Wrought Iron

• Steel

• Concrete

• Stainless Steel

1. Timber (2 Advantages + 2 disadvantages)

Advantages

• Offered ease of manufacture

• Readily available resource

Disadvantages

• Rots away easily

2. Stone (1 advantage + 1advantage)

• Strong in compresion, weak in tension

• Durable

3. Brick

• Strong in compression

• Weak in Tension

• Same as stone

• Occasionally used in bridge construction.

4. Cast Iron (strong compres, melte and cast, reduce weigh..)

• Strong in compression but weak in tension

• It can be melted and cast, saving time and money.

• Greatly reduced weight

5. Wrought Iron (where was it used in)

• Earlu suspension bridges

Wrought Iron disadvnatage - (unreliab… due to its fibr

• Unreliable due to its fibrous ferrite structure, tended to weaken it

When Wrought Iron was replaced by steel suspension….

suspension bridges could be built more longer

Steel (when founded and who)

• 1856 Henry Bessemer

Steel ( 2 advantage, used in…)

• Strong in Tension, Compression, Malleable and easy to construct with

• Enabled construction of much greater spans.

• Used in arch bridges, steel cables for suspension bridges, and reinforced concrete.

Concrete - not used until…

• Was not used in bridge construction until shrinkage problem was adressed by 3rd Hinge

• Strong in compression but weak in tension.

• Pre-stressed and post-stressed concrete are commonly used in modern bridges.

Stainless Steel

• Used for corrosion resistant and pedestrian bridges

Enviromental Implications of Materials used in Civil Structure

Timber

• Resulted in deforestation of the surrounding area

• Trees take centuries to grow

Stone

• Had to mine stone, digging large quarries

• Impacting fauna and flora and damaging ecosystem

Bricks (subsidence meaning

• Bricks require large amounts of clay and shale to manufacture, similar to stone

• Subsidence: The ground sinks or settles, which can be a problem at old brick pit sites.

Cast and Wrought Iron

• Fossil fuel combustion for smelting cast and wrought iron caused environmental degradation.

• Required mining and smelting of iron, which damaged the landscape.

Steel

• Fossils fuel combustion and mining - SIMILAR TO CAST AND WROUGHT IRON

• Enabled longer bridges with fewer piers, reducing disruption to waterways.

Concrete

Requires large amounts of minerals to manufacture, causing environmental damage.

Societal Advancements (steel and concrete enab larger…

Steel and concrete enabled larger, stronger, and more durable bridges, improving infrastructure and connectivity significantly.

Engineering Mechanics

VERY IMPORTANT TABLE - COMING IN EXAM (Supports for beams or trusses)

Support 1: ___

Fixed

Freebody diagram of “Fixed Support” + ATTRIBUTES

• Can support

VERTICAL

HORIZONATAL

MOMENTS

Reason for use (to firmly ancho… a strcy

• To firmly anchor a structure

Support 2: ___

• Hinge/ Pin

FBD of hinge + attributes (free to rotat…

• Vertical

• Horizontal

• Free to rotate

Reason for use (To provide a non movin… supp for

• To provide a non moving support for a bridge

Support 3_____

• Roller

FBD + Attributes

• Only reaction normal to surface

• free to rotate

Reasons for use ( to allow side movemen for expansio in tru.)

• To allow side movement for expansion in truss

Engineering Materials

Testing of Materials

• Allow us to watch and analyse material behaviour under load

• Non Destructive testing

• Destructive testing

Non Destructive Testing (X, DP, U)

• X ray

• Dye Penetrant

• Ultrasonic

X- RAY (USE AND METHOD) - passed throu, expose on a photosen, locartion can be fou

USE: X rays are used to locate the cavaties

METHOD

1. X-ray passed through material/object

   and exposed onto a photosensitive film

   on the opposite side.

2. The location of cavities and internal

   faults can be found.

Diagram of X-Ray Testing

2. Dye Penetrant Testing (USE AND METHOD)

(remo oi, area heat and dy, wip, devel, coo dow, dye squee ou)

Use: To determine if cracks are present in metallic items

METHOD

1. Remove any oil or surface contaminents in the area

2. Area is heated and dye is placed over the surface

3. Wipe of excess

4. A developer (white powder) sprinkled on the area

5. Then cooled

6. If crack is present, dye will be squeezed out by the contraction of cooling item

How can you spot cracks more visbly undeer DYE PENETRANT TESTING

• UV Light

3. Ultrasonic Testing (use and method)

(metho: high f radi sent by tran throu comp, refl sig show the cav

USE: Determining the location of cavities.

METHOD:

1. High freqency radio waves are sent by the transmitter through components

2. The reflected signals show the results

   of any cavities on the surface.

Deconstructive/ Concrete Testing (T, C,T, T, S)

• Tensile

• Compressive

• Transverse

• Torsion

• Slump

1. Tensile Test

• Used to determine tensile test

Method

1. A testing machine stretches a piece of

   material.

2. The elongation and load are recorded as it breaks

2. Compressive test

• Used to determine compressive strength of material

Method

1. A piece of material is crushed by a

   testing machine

2. The deformation and load are recorded

   as it breaks.

Effect of Testing concrete for compreesive tests (if it fails)

• If the concrete fails compression test, material was faulty and may need be to removed, being expensive and time consuimg

Transverse Test (when ben, method: support both end, measure of bending lo at rup)

• Used to determine how a material peform when bent

Method

1. . Material is supported on both ends and a load is applied on oppiste side

2. Measure of bending load and total deflection at rupture

Torsion Test

• How well a material copes with twisting forces

Slump Testing (USE, METHOD AND if it collapses= , if ir cracks=

• Measures the workability of concrete more specifcally fluidity

Method

1. The concrete is cast into a conical mould

2. Wet Concrete poured in

If it collapeses = TOO WET

If it cracks= TOO DRY

Bending Stress

A positive bending beam (whagt does it consits of)

• Ends are up and centre is down

Upper surface will undergo…

COMPRESSION

Lower surfaces will be in….

Tension

The greater the distance from the neutral axis the greate…

The stress present

Formula for Bending Stress

• BENDING STRESS= Moment y / I

3 formulas (3 fractions to represent)

• M/I = E/R = BENDING STRESS/Y

What is “E”

Young Modulus (PA)

What is “I”

Second moment of area

What does “I” Measure

• The second moment of area measures the resistance of the beams cross section to bending

More I=, Less I

• Better for bending as more resistant

Less I= worse as it is bent easily

N/ m 2 (what unit) vs N/mm 2

• N/m2 = PASCALS

• N/mm2= MEGA PASCAL

I Beams (cross section w greater d then b, high strenth to wei ra, making it eff to resi bend)

• Has a cross section with greater depth then breadth, high strength-to-weight ratio, making it efficient at resisting bending forces.

Uniformly Distributed Loads

• A load that is uniformly spread across a beam

Example of UDL (win agaiant bui, fihs tank on she)

• Wind blowing agaisnt a building

• Fish tank on a shelf

Know how it looks like