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
To illustrate their relationship, let’s consider the following equation relating
to beam curvature:
Curvature = 1/r = e/(d-x)
where r = radius of curvature
e = tensile strain in tension reinforcement
d = effective depth
x = depth of neutral axis
Provided that the tensile strain in tension reinforcement remains constant,
the curvature of concrete structure increases with the depth of neutral axis.
It is observed that the depth of neutral axis rises with tension steel ratio.
Therefore, the curvature of concrete section is directly proportional to the
tension steel ratio. In addition, the larger value of the depth of neutral axis
enhances increased area of concrete compression so that the effect of
creep on deflection appears to become significant.
10. For column reinforcements, why is helical reinforcement
sometimes designed instead of normal links?
The use of links for column design in Britain is very popular. However, in
U.S.A. engineers tend to use helical reinforcement instead of normal links
because helical reinforcement has the potential advantage of protecting
columns/piles against seismic loads. Moreover, when the columns reach
the failure state, the concrete outside hoops cracks and falls off firstly,
followed by the eventual failure of the whole columns. The peeling off of
concrete outside helical reinforcement provides a warning signal before the
sudden failure of columns as suggested by G. P. Manning (1924). In
addition, it can take up a higher working load than normal link
reinforcement.
For instance, helical reinforcement is adopted in the design of marine piles
in Government piers.
Note: Helical reinforcement refers to shear reinforcement which is spiral in shapes.
11. What is the effect of rusting on steel reinforcement? (SR4)
The corrosion of steel reinforcement inside a concrete structure is
undesirable in the following ways:
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