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
would be separated from the beams and there would be lesser
deceleration experienced by the vehicles [48].
Fig. Beam barrier.
3. Why is concrete crash barriers normally used in central divider?
(CPB2)
Concrete crash barriers are not considered as the best barrier design
because of the following reasons when compared with flexible barriers:
(i) Concrete barriers possess rough surface which, when impacted by
moving vehicles, tend to cause considerable damage to the vehicles.
(ii) Since concrete is a rigid material and the deceleration of collided
vehicles is comparatively large when compared with flexible barriers.
However, concrete crash barriers have particular application in locations
where the deflection of barriers is not allowed. For instance, in the central
divider of a carriageway, if flexible barriers are adopted and vehicles crush
into the barriers, the deformation resulting from the hitting of vehicles would
result in an intrusion to the adjacent carriageway. This is undesirable
because this may trigger further collisions in the adjacent carriageway and
hence rigid barriers like concrete crash barriers should be adopted in this
scenario.
4. What is the difference between safety fence and safety barrier?
(BT1)
A safety fence is intended to absorb some energy caused by hitting
vehicles and to realign the vehicles to move parallel to the safety fence.
A safety barrier is intended to provide containment instead of energy
absorption upon hit by vehicles. Hence, it is anticipated to have little
deflection and deformation only. After crashing, it serves to re-direct the
vehicles along the line of barrier.
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