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ENGINEERING, CS 2025 HSC 22b

A building is being partially demolished and replaced. Part of the original structure will be retained.

Engineers want to retain some steel components of the building.

Describe a suitable process which could be used to detect surface cracks in ONE steel component of the building.   (3 marks)

Show Answers Only
  • Magnetic particle inspection (MPI) is a non-destructive testing method suitable for detecting surface cracks in steel components.
  • The steel component is first cleaned and then magnetised using an electromagnet or permanent magnet. Iron oxide particles suspended in a liquid carrier are then applied to the surface.
  • Where surface cracks exist, magnetic flux leaks outward and attracts the particles, forming a visible cluster that clearly marks the location and extent of any defect.
  • The component is then inspected under white or ultraviolet light, and the severity of any cracking is assessed before a repair or replacement decision is made.
Show Worked Solution
  • Magnetic particle inspection (MPI) is a non-destructive testing method suitable for detecting surface cracks in steel components.
  • The steel component is first cleaned and then magnetised using an electromagnet or permanent magnet. Iron oxide particles suspended in a liquid carrier are then applied to the surface.
  • Where surface cracks exist, magnetic flux leaks outward and attracts the particles, forming a visible cluster that clearly marks the location and extent of any defect.
  • The component is then inspected under white or ultraviolet light, and the severity of any cracking is assessed before a repair or replacement decision is made.

ENGINEERING, CS 2018 HSC 10 MC

In a ductile material, which two stresses are used to calculate the factor of safety (FOS)?

  1. Working and yield
  2. Working and compressive
  3. Bending and yield
  4. Bending and compressive
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`A`

Show Worked Solution
`sigma_(text{allowable})` `= sigma_(text{yield})/text{FOS}`  
`text{FOS}` `= sigma_(text{yield})/sigma_(text{allowable})`  
     
  • `sigma_(text{allowable})` is working stress.
  • FOS is calculated using yield and working stress in ductile materials.

`=>A`


♦ Mean mark 42%.

ENGINEERING, CS 2019 HSC 21c

A bus shelter is shown.

   

Describe a testing procedure that could be used to determine the structural strength of the laminated timber beam. Support your answer with a labelled sketch.   (4 marks)

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Traverse Bend Test

  • Used to measure the beam’s flexural strength.
  • A single or double point load is applied to a beam supported at both ends.
  • The measured deflection is plotted onto a load/deflection graph.
     

Show Worked Solution

Traverse Bend Test

  • Used to measure the beam’s flexural strength.
  • A single or double point load is applied to a beam supported at both ends.
  • The measured deflection is plotted onto a load/deflection graph.
     


♦ Mean mark 39%.

ENGINEERING, CS 2019 HSC 9 MC

A sketch of a post-tensioned concrete beam is shown.
 

Which of the following shows the most likely loading condition the beam is designed to resist when viewed from the front?
 

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`D`

Show Worked Solution
  • Concrete has high compressive strength, while the steel reinforcements have high tensile strength.
  • Hence, the most likely loading scenario will put the bottom of the beam in tension and the top in compression. 

`=>D`

ENGINEERING, CS 2020 HSC 9 MC

A cured cylindrical concrete specimen is tested under a compressive load through its vertical axis, until it fails.
 

Which of the following is the most likely shape of the front view of the failed specimen?
 

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`A`

Show Worked Solution
  • There are 3 common fracture patterns in concrete under compressive testing.
  • Of the options given, `A` is the only one displaying an example of these patterns.

`=>A`


♦♦♦ Mean mark 14%.

ENGINEERING, CS 2021 HSC 17 MC

Which of the following is a specialised test used to determine the compressive strength of cured concrete?

  1. Slump test
  2. Janka hardness test
  3. Shore hardness test
  4. Rebound hammer test
Show Answers Only

`D`

Show Worked Solution

Considering each option:

  • Slump test – tests the workability and consistency of wet concrete.
  • Janka hardness test – tests hardwood flooring.
  • Shore hardness test – tests soft elastomers and other soft polymers.
  • Rebound hammer test – tests the compressive strength of cured concrete.

`=>D`

♦♦♦ Mean mark 19%.