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This unit addresses aspects of the following syllabus outcomes:

H1.2 differentiates between properties of materials and justifies the selection of materials, components and processes in engineering

H2.1 determines suitable properties, uses and applications of materials in engineering

H4.1 investigates the extent of technological change in engineering

H4.3 appreciates social, environmental and cultural implications of technological change in engineering and applies them to the analysis of specific problems

H6.1 demonstrates skills in research and problem solving related to engineering.

Source: Board of Studies NSW (1999) Stage 6 Syllabus, engineering studies, preliminary and HSC courses. Board of Studies: Sydney.

Bridge 1 Bridge 2 Bridge 3
Bridge 1 Bridge 2 Bridge 3
Bridge 4 Bridge 5 Bridge 6
Bridge 4 Bridge 5 Bridge 6
Bridge 7 Bridge 8 Bridge 9
Bridge 7 Bridge 8 Bridge 9

The images shown above represent some of the different types of bridges built over time. Use these images, and some of the web sites included in this unit to answer the questions provided.

Some significant details of bridge 6, the Sydney Harbour Bridge, can be found at http://www.sydneyharbourbridge.info Selecting this link will take you to an external site.

Question 1

Using the following terms, classify each bridge as a mechanical system, by completing the following table.

Mechanical system Bridge number
Beam/girder  
Truss  
Arch  
Suspension  

Now use your web browser to find the web site at: http://www.brantacan.co.uk/bridges.htm Selecting this link will take you to an external site. to find out more about each of these types of bridge.

Answer

Question 2

Which of the bridges shown use a combination of these mechanical systems? What are the combinations?

Answer

Question 3

Bridges 1 and 2 were mostly made from naturally occurring materials. What are the major materials innovations used for each of the other types of bridges listed in the table below?

Bridge number Materials innovation
4  
5  
6  
7  
8  
9  

Answer

Question 4

The main loads that act upon bridges are those that come from the:

Complete the following table by giving the angle and placing a cross in the relevant cell(s):

Source Angle Live Dead Point UDL
Mass          
Traffic          
Reactions          
Wind          

Answer

Question 5

This picture shows how the loads on an arch bridge are transferred to the abutments for support

Diagram 1

The diagram above shows how the loads on an arch bridge are transferred to the abutments for support. Using a simple sketch of your own, show how loads on a beam bridge and a suspension bridge are transferred to the abutments.

Answer

Question 6

  1. Why is it necessary on some bridges to use roller or sliding bearing supports?

  2. What type of force reactions occur at:
    • roller bearings
    • fixed bearings
    • sliding bearings.

  3. What is another type of bridge support?

Answer

Question 7

  1. The drawing below represents the frame of a simple pin jointed truss that could be used for a bridge design. Calculate the reactions at A and D if the total live and dead loads are equivalent to 200 kN acting on the centre joint.

    This drawing represents the frame of a simple pin jointed truss that could be used for a bridge design

  2. Use the method of sections to calculate the force developed in member BC in the truss above.

The method of sections uses the principle that if the whole structure is in equilibrium, then any one component, or group of components must also be in equilibrium.

Answer

Question 8

  1. What is meant by the term “Factor of safety”?
  2. Member BC in the truss is made from square section Grey Gum timber with a compressive (crushing) strength of 82 MPa. A factor of safety of 1.5 is required in the truss design. Calculate the minimum cross-sectional size for this member.

Answer

Question 9

An RSJ made from structural steel might be suitable as a structural member in bridge 5.

  1. How would this type of beam be manufactured?
  2. What is the composition of structural steel?
  3. What is the microstructure of structural steel?

Answer

Question 10

Reinforced concrete is used to construct bridges 7, 8 and 9.

  1. What are the constituents that are used to make concrete?
  2. What is the function of the steel reinforcement in concrete beams and slabs?
  3. Why is the position of the steel reinforcement in the concrete very important?
  4. Why is corrosion a significant issue in reinforced concrete?

Answer

Question 11

Asphalt is frequently laid on concrete as a road surface.

  1. What properties make asphalt suitable as a road surface material?
  2. Why is asphalt known as a composite material?
  3. What are the phases present in the structure of asphalt?

Answer

Question 12

Describe the process and advantages of using post-tensioning in bridge construction.

Answer

Other useful resources:

You can find out some detail on a wide range of different types of civil structures from across the world at the following web site. The site is an international database and gallery of structures. Just select the relevant site from the alphabetical index:

These two sites allow you to study various types of bridge structures from around the world:

The following sites provide some detail on other types of civil structures such as dams, tunnels and skyscrapers:

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