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Engineer’s Memos
Why PermaDock Excels in a Heavy Surge Environment
                               The Conditions are
         Stability, Survivability, and Impact Loads

The stability of a dock increases as the square of its beam.  A three foot wide
dock is one seventh as stable as an eight foot wide dock.  Whether the dock
is wooden, made of palm fronds, or concrete, a three foot dock Is one seventh
as stable as an eight foot dock.

A dock being pushed by a wall of water (wake from an 80 footer, tidal surge or
tsunami) is being impacted by a large amount of energy, which must be
counteracted, usually by the pilings or by flex, in accordance with the material’s
design criteria or otherwise.  The energy of the dock doubles when the weight
doubles, but it increases four times when the speed of the water doubles.  

Impact Loads
Try to push a nail into wood with your palm and nothing happens.  But give it a
good whack with a hammer and you’ll see how “impact” amplifies the load.  
Lateral impact loads can be very destructive to structural members, particularly
at the fasteners.  Each flex event wears down the wood at the fasteners,
making the system unstable.
                                            The Cures are to
      Reduce Mass, Reduce Draft, and Absorb Shock

Reduce Mass
In a heavy surge or tsunami environment, a marina system’s heavy mass can be a
significant detriment because It generally increases draft.  Additionally, the materials
used in a ‘heavy’ dock system - wood or concrete - do not have the memory of a
Permadock system, so once they experience extreme lateral forces, they’re
damaged,and will remain that way.  

Reduce Draft
This is probably the most important cure.  In short, when designing a marina for a
heavy surge environment, it is better to have a dock that floats on the water rather
than in the water!  A deep draft will create enormous drag, which puts an enormous
load on the system’s weak points.  Just watch the YouTube videos from the
Crescent City, California tsunami damage in March 2011 to see how heavy mass
and deep draft can work to the disadvantage of a dock under severe lateral stress.

Absorb Shock
Impacts should be absorbed as much as possible.  First, the entire system should
be able to flex without causing damage and return to original shape.  PermaDock’s
patented, skin-stressed design allows the materials to do this, and without
deterioration.  Second, PermaGrip Piling Stabilizers isolate the flexible dock from
the fixed piling through a patented spring system which dampens impacts and stops
“banging”.  Third, PermaPile Elastomer Pilings absorb huge loads through built-in
flexibility.  The combination of the PermaDock design, PermaGrip Piling Stabilizers
And PermaPile Elastomer Pilings combine to form a system which can achieve
performance results that have been unheard of previously.  And it looks great!