In designing dolphins, they are normally supported on a system of three to four raking piles. This in essence is a rigid structure and exhibits little flexibility e.g. movement against impact and berthing loads by vessels. In fact, this kind of design may not be desirable in terms of maintenance because the dolphins are readily susceptible to damage by high berthing vessels.
To rectify this situation, some energy absorption devices like rubber/plastic fenders have to be installed to reduce the impact load deriving from its own deflection. On the other hand, by designing dolphins as flexible structures capable for allowing slight deflection, it helps to reduce the large forces generated during berthing of vessels. In this connection, one way of designing dolphins as flexible structures is by provision of a single pile only.
Note: For a rigid structure, it takes up external loads without undergoing excessive deformations.
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