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
two available methods, engineers should make their own judgments based
on the above considerations.
Fig. Y-junction in drainage pipes.
20. Should the distribution of reinforcement be designed as uniform
for concrete surround of drainage pipes? (ED4)
Concrete surround is normally adopted for rigid drainage pipes to resist
high traffic loads (e.g. under shallow covers) and to allow for using pipes
with lower strength. Moreover, the use of concrete surround can minimize
settlement of adjacent structures. In addition, the highest possible
accuracy in levels and gradient can be achieved by using concrete
surround as considerable settlement is expected in other types of beddings
like granular bedding.
The distribution of reinforcement in concrete pipes may not be uniform
owing to the occurrence of tensile stresses in different locations around the
circumference of the pipes [67]. For instance, tensile stresses are highest
at the inner face of pipes at invert and crown levels and at the outer face of
the two sides of pipes. An elliptical cage may be designed in order to
optimize the usage of steel reinforcement.
Fig. Concrete surround of drains.
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