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
supported by stringer beams. For the case of sidewalls, it acts as a
cantilever beam and the main reinforcement are provided the top surface
of slab. For the case of staircase supported sideways by both sidewall and
stringer beam, it should be designed transversely with end supports as
sidewall and stringer beam and reinforcement is provided at the bottom of
the staircase.
(iii) Stairs resting on solid support
For stairs resting on solid supports, only nominal steel reinforcement is
provided to control thermal and shrinkage cracking.
15. Why are voids filled with lightweight infilling material in raft
foundation of pumping stations? (PS4)
To reduce the dead load and hence to reduce the settlement of pumping
stations, the voids inside the raft foundations are filled with light material. If
instead concrete is placed inside these voids, it poses severe thermal
cracking problem and drastically increases loads to pumping stations. The
use of general fill is also not desirable because its self-weight is
comparable to that of concrete. On the contrary, if these voids are left
vacant, water may penetrate into these voids during future operation and
increases the dead load of pumping stations during its normal operation.
Therefore, lightweight infill material, which is non-water-absorbing and
non-biodegradable, is designed inside these voids to avoid ingress of
water and to reduce the dead load of the structure.
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