The Final Test… Before the opening ceremony in 1859, the

Victoria Bridge underwent a safety test.

The test consisted of an 18 platform cart train filled to capacity with rocks crossed the bridge. The train and load weighed about 1 ton/foot.

The two locomotives hired to pull the train across were insufficient and a third was required.

In spite, of all this weight, the deflection (bending) of the bridge was a little over 1 inch and returned to normal as the load was removed.

The Victoria BridgeA quick overview of the Tubular design

Situation

The Victoria Bridge was a technological marvel, yet the engineers in charge knew less about materials than we do today.

Justify which material you would have chosen for the project.

What to consider?What should one consider before

selecting the construction materials?

What to consider? What are the stresses/external forces the

material will undergo? (Constraints)

How do we want the material to react to such stresses? (Deformation)

How will the material react? (Material properties)

Will the material last a long time? (Degradation)

Constraints

What external forces are at play?

ConstraintsA constraint is the effect external forces

have on a material/object/system.

Examples of constraints: Pulling an elastic band Squishing a sponge

Types of ConstraintsThere are 5 main types of constraints

Compression Tension Torsion Deflection Shearing

Using the definitions soon to be provided, can you give a common everyday example for each of these constraints?

Types of constraintsCompression:

When a material is subjected to forces that tend to crush it

Tension When a material is subjected to forces that

tend to stretch it

Types of ConstraintsTorsion

When a material is subjected to forces that tend to twist it

Shearing When a material is subjected to forces that

tend to cut it

Deflection When a material is subject to forces that

tend to bend it

Types of Constraints Which constraints would a bridge most likely

be subjected? Explain your reasoning.

5 Constraint reminder: Compression Tension Torsion Shearing Deflection

Deformation

Ways that materials react to the constraint

Deformations A material deformation is the change in

shape of a material based on the constraints that are applied.

There are three main types of deformations Elastic Plastic Fracture

Using the definition soon to be provided, can you give a common everyday example for each of these deformations?

Types of material deformationElastic:

When the constraint leads to a temporary change in the shape or dimensions of the material.

When the constraint is removed, the material returns to its original form.

Types of material deformationPlastic:

The constraint leads to a permanent change in the shape or dimensions of the material.

Even when the constraint is removed, the material remains deformed

Types of Material Deformation

Fracture: The constraint is so intense that it breaks

the material

Types of DeformationsWhat are some of the deformations that

a bridge is likely to undergo?

Explain your reasoning.

Properties

Characteristics that will help determine how a given material will react to a constraint.

Properties The reaction of a material to constraints depends on

its mechanical properties.

Types of Mechanical Properties: Hardness Elasticity Resilience Ductility Malleability Stiffness

Which properties do you believe were considered in the selection of the building material for the Victoria Bridge?

Definition of mechanical properties

Hardness Ability to resist indentation

Elasticity: Ability to return to their original shape

Resilience: Ability to resist shocks

Ductility: Ability to be stretched without breaking

Malleability: Ability to be flattened or bent without breaking

Stiffness: Ability to retain their shape when subjected to

many constraints

Definition of mechanical properties

A material can also undergo chemical changes, such as rusting and corrosion.

What kind of properties should a bridge possess?

Other propertiesResistance to corrosion:

Ability to resist the effects of corrosive substances which cause the formation of rust, for example.

Electrical conductivity: Ability to carry an electric current

Thermal conductivity: Ability to transmit heat

Degradation

How will a material age?

DegradationThe degradation of a materials is the

decline in some of its properties due to its environment or time

Degradation of the Victoria Bridge

In 1897 the Victoria bridge was renovated To accommodate the increase in the

demand of transportation To repair the degradation of the bridge’s

superstructure. The piers only required minor changes.

Common materials used in the 1800’s

Wood Wood is a ligneous (fibrous) material whose

bark has been removed.

The mechanical properties differ depending on the type of wood

Two types of wood Hardwood (deciduous trees)

More resistant to wear and harder than softwood Softwood (coniferous trees)

Wood (general properties)Hardness, elasticity, resilienceLow thermal conductivityEasily shaped and assembledLight weight

Would these properties be useful during the construction of a bridge?

Wood degradationDue to its organic nature, fungus,

insects and micro-organisms can infest the wood.

By varnishing, painting or treating the wood, we can extend its lifetime.

MetalsMetals are not usually used in their pure

form, but are combined with other substances to improve their properties.

This mixture is called an alloy (homogeneous mixture of two or more metals)

Metals (properties)The properties vary on the metal used

Out of the list provided to you, which metal or alloy would you consider in the construction of the Victoria Bridge. Justify your answer.

Please keep in mind… The Victoria bridge is a Tubular Bridge

It is 6 592 feet in length

The superstructure alone weighed 9044 tons. That is 8 204 578.79 kg

Due to the use of the steam engine, temperatures inside the tube could reach up to 125 F That is 52 Celsius

Metals Description Properties Cost *

Aluminum White Malleability 2.508$/kg

Soft Lightness

Abundant in nature Resists corrosion

  Very good electrical conductor

Iron Silver in color Ductility 0.21$/kg

Can rust in the presence of Oxygen

Malleability

Nickel Grey Hardness 1.43$/kg

Malleability

Resists Corrosion

Tin Silvery white Ductility 16.214$/kg

Malleability

Relatively low melting point (239C)

Alloys Description Properties Cost*

Cast iron (iron and carbon mixture)

Made of more than 2% carbon

Hardness 0.18$/kg

Steel (iron and carbon mixture)

Made of less than 1.5% carbon

Hardness 0.52$/kg

Resilience

Malleability

Brass (copper and steel)

Mixture of copper and steel

Color varies according to mixture

  

Ductility 2.37$/kg

Malleability

Resists Corrosion

Excellent electrical conductivity