A Self-Learning Manual - Institution of Engineers Mauritius

A Self-Learning Manual
Mastering Different Fields of Civil Engineering Works (VC-Q&A Method) Vincent T. H. CHU
Level Two (Advanced FAQs)
Part I: Miscellaneous
1. What is the reason of grouping several reinforcement bars in
concrete structure? (SR1)
For too much reinforcement to be incorporated in concrete structures, the
reinforcement bars are sometimes groups because:
(i) It facilitates placing of fresh concrete with more space available;
(ii) It tends to limit segregation , which otherwise caused by close
spacing of bars;
(iii) It ensures good cover.
2. What is the purpose of conducting bend test of reinforcement?
(SR2)
It is not uncommon that steel reinforcement is bent prior to installation into
concrete structure. However, upon bending process steel reinforcement
may fracture owing to the following reasons:
(i) The ribs on steel bars serve as location of stress concentration
which is a potential weak point for fracturing.
(ii) Owing to their intrinsic high strength, large force is required during
the bending process.
(iii) The radius of bending is too tight.
Temperature is also an important factor for controlling the risk of steel
fracture. The risk of fracture is increased when there is a drop of
temperature because steel has lower toughness at low temperatures.
Therefore, bend test are carried out for reinforcing steel to testify their
bending performance.
3. What is the purpose of conducting re-bend test of steel
reinforcement? (SR3)
In BS4449:1997 it species a re-bend test of steel reinforcement where
reinforcing steel is bent 45 o at 100 o C for an hour and then bent back by 23 o .
The purpose of re-bend test is to measure the effect of strain ageing on
steel. Strain ageing has embrittlement effect which takes place after cold
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