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
leaving both piers in compression. As such, this allows for the use of
pinned bearing. The optimum spacing of twin piers is about 1/25 to 1/13 of
adjacent span.
10. What is the purpose of providing a barrier around the bridge
piers?
Accidental collision of heavy vehicles such as tractor-trailer with bridge
piers is not uncommon around the world. The consequence of such
collision is catastrophic which may involve the collapse of bridges and loss
of human lives. As such, suitable provisions are made to protect bridge
piers against these accidental collisions. The most common way is to
install a crashworthy barrier which should be designed to be capable of
resisting the impact of heavy vehicles. Alternatively, in some countries such
as the United States, they tend to revise the design of bridge barriers by
requiring the bridge piers to be able to resist the collision of 1,800kN static
force at 1.35m above ground.
11. In bridge columns, why are stirrups be placed around the vertical
reinforcement?
In uniaxial compression test of concrete, upon reaching the ultimate load
failure of concrete occurs where major cracks line up in the vertical
direction and the concrete cube would be split up. The development of
vertical cracks involves the expansion of concrete in lateral directions. In
case the concrete is confined in lateral directions, it was observed that the
formation of vertical cracks would be hindered as indicated in past
experiments. As a result, the concrete strength is increased with also a rise
in failure strain.
The above theory is often used in the design of bridge columns. Steel
stirrups are installed at around the vertical main reinforcement. Other than
the function of shear reinforcement, it helps to avoid the lateral deformation
of interior concrete core so that the strength of concrete column is
increased.
12. What are the effects of bridge piers across a stream?
The presence of bridge piers across a stream causes constricted flow in
the openings because of the decrease of width of stream owing to the
presence of the piers. Moreover, it creates the following problems from
hydraulic point of view:
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