A Closer Look at Prevailing Civil Engineering Practice - European ...

A Closer Look at Prevailing Civil Engineering Practice, What, Why and How
Vincent T. H. CHU
material. These heavy equipment could generate very high impact load
with short duration on the concrete pipes. It requires an extremely even
and uniform support in order to safely support these loads. Therefore, it is
not uncommon that construction vehicles are primary source of
crack-producer and it usually results in the formation of circumferential
cracks.
3. What is the difference between on-seating and off-seating head in
penstock
A penstock is commonly used to control the flow and water level and for
isolation of fluid. It mainly consists of a sliding door which is controlled by
mechanical spindle moving through a hole in a frame built onto a structure.
Penstock is the term used in UK while sluice gate is more commonly
adopted outside UK. In the design of penstock, it is important to identify if it
would take on-seating head or off-seating head.
On-seating head refers to the water pressure forcing the penstock into the
wall while off-seating head refers to the water pressure forcing the
penstock out of the wall as shown below.
Fig. 3.2 On-seating (left) and off-seating head (right)
4. Should the same freeboard be maintained along a channel
The freeboard is defined as the vertical distance from water surface to the
top of channel bank. The selection of freeboard is dependent on the
consequence should overflow out of channel bank occurs. Other than that,
consideration should also be given to prevent waves, superelevation and
fluctuations in water surface from overflowing the channel banks.
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