Wave Attenuation
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Transcript of Wave Attenuation
PIER 4 CONDOMINUMS PIER 4 CONDOMINUMS Dock and Wave Dock and Wave
Attenuator replacement Attenuator replacement proposalproposal
Presented by Presented by
Bellingham MarineBellingham MarineJune 29June 29thth. 2005. 2005
Existing Conditions at Pier 4 Condominiums:
What’s the COST of a Wave
Attenuator?
Wave Attenuators are the Wave Attenuators are the most site specific most site specific
designed structures in a designed structures in a marina.marina.
Can’t you give me a
SQUARE FOOT NUMBER?
Different shapes and mass;
Different Drafts
Different Widths.
How do I know what size How do I know what size and shape attenuator I and shape attenuator I
need?need?
Determine Design Wave relevant to YOUR site.
Wind Generated Waves
Wake Generated Waves
How does God make waves?How does God make waves?
WIND!WIND!
Wind blows, creating friction Wind blows, creating friction on the surface of a body of on the surface of a body of
water. water.
What Factors Create and Effect Wind Generated
Waves?
Wind Duration
Wind Speed
Fetch
Water Depth
Fetch (n) : a) The distance over which a wind blows. b) The distance traveled by waves with no obstructions
Wind Speed – The average wind velocity over a 3 second gust.
Wind Duration – The length of time the wind blows in minutes or hours.
Water Depth – The depth of the water during the wind event.
How does Man make waves?How does Man make waves?
BOAT WAKES!BOAT WAKES!
Boat Wakes: Under certain conditions the prevailing
cause of waves incident to a facility could be boat wakes. They are more frequent than extreme wave events
and will lead to structural deterioration by cyclic fatigue.
Factors Used to Determine Vessel Wake Size
Boat Length
Boat Displacement
Boat Speed
Boat Hull Shape
Channel Distance to Site
DETERMINE THE DESIGN WAVE
• Once the two different types of waves are evaluated the attenuator Design Wave is determined by identifying the governing load case.
• The Design Wave parameters are identified; which include the wave height, wave length and wave period.
The right size and configuration The right size and configuration of a attenuator will create a calm of a attenuator will create a calm
basin for basin for this specific site.this specific site.
=
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√≈
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1.0 .9 .8 .7 .6 .5 .4 .3 .2 .1 0 .1 .2 .3 .4 .5 .6
B/L using a 12’ breakwater
Kt
WAVE TRANSMISSION TABLE GIVEN WAVE PERIOD AND ATTENUATOR WIDTHS PERIOD LENGTH WIDTH 8 9 10 11 12
3.5 63 0.13 0.14 0.16 0.18 0.19 3.25 54 0.15 0.17 0.18 0.20 0.22
3 46 0.17 0.20 0.22 0.24 0.26 2.75 39 0.21 0.23 0.26 0.28 0.31 2.5 32 0.25 0.28 0.31 0.34 0.38
So for Hs = 3.0 as shown in the Wave Tank example; KT will as shown below PERIOD LENGTH WIDTH 8 9 10 11 12
3.5 63 0.55 0.45 0.42 0.40 0.38 3.25 54 0.50 0.41 0.40 0.38 0.34
3 46 0.41 0.38 0.34 0.31 0.30 2.75 39 0.36 0.32 0.30 0.29 0.28 2.5 32 0.31 0.29 0.28 0.27 0.28
So for Hs = 3.0 as shown in Wave Tank example; Hs = 3.0 HT will as shown below PERIOD LENGTH WIDTH 8 9 10 11 12
3.5 63 1.65 1.35 1.26 1.20 1.14 3.25 54 1.50 1.23 1.20 1.14 1.02
3 46 1.23 1.14 1.02 0.93 0.90 2.75 39 1.08 0.96 0.90 0.87 0.84
1.0 .9 .8 .7 .6 .5 .4 .3 .2 .1 0 .1 .2 .3 .4 .5 .6
B/L using a 12’ breakwater
Kt
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