ISO 21650:2007
(Main)Actions from waves and currents on coastal structures
Actions from waves and currents on coastal structures
ISO 21650:2007 describes the principles of determining the wave and current actions on structures of the following types in the coastal zone and estuaries: breakwaters: rubble mound breakwaters; vertical and composite breakwaters; wave screens; floating breakwaters; coastal dykes; seawalls; cylindrical structures (jetties, dolphins, lighthouses, pipelines etc.). ISO 21650:2007 does not include breakwater layout for harbours, layout of structures to manage sediment transport, scour and beach stability or the response of flexible dynamic structures, except vortex induced vibrations. Design will be performed at different levels of detail: concepts; feasibility; detailed design. ISO 21650:2007 is aimed at serving the detailed design.
Effets des vagues et des courants sur les structures côtières
General Information
Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 21650
First edition
2007-10-15
Actions from waves and currents on
coastal structures
Effets des vagues et des courants sur les structures côtières
Reference number
ISO 21650:2007(E)
©
ISO 2007
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ISO 21650:2007(E)
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ISO 21650:2007(E)
Contents Page
Foreword. iv
Introduction . v
1 Scope . 1
2 Terms and definitions. 2
3 Symbols . 9
4 Basic variables for actions from waves and currents . 9
4.1 Water levels . 9
4.2 Waves. 10
4.3 Currents . 13
5 Wave and current action on structures. 13
5.1 Wave action on mound breakwaters .13
5.2 Wave action on vertical and composite breakwaters . 16
5.3 Wave actions on coastal dykes and seawalls . 17
5.4 Wave and current action on cylindrical members and isolated cylindrical structures. 20
5.5 Wave interaction with floating breakwaters. 21
5.6 Wave action on wave screens . 22
6 Probabilistic analysis of performance of structures exposed to action from waves and
currents. 23
6.1 Examination of uncertainties related to wave and current action. 23
6.2 Reliability assessment of structures . 24
Annex A (informative) Water levels . 25
Annex B (informative) Wave action parameters. 27
Annex C (informative) Currents . 41
Annex D (informative) Wave action on rubble mound structures. 43
Annex E (informative) Wave actions on vertical and composite breakwaters. 63
Annex F (informative) Wave action on coastal dykes and seawalls . 68
Annex G (informative) Wave and current actions on cylindrical members and isolated structures. 76
Annex H (informative) Wave interaction with floating breakwaters. 93
Annex I (informative) Wave action on wave screens. 97
Annex J (informative) Probabilistic analysis of performance of structures exposed to action from
waves and currents . 102
Bibliography . 112
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ISO 21650:2007(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 21650 was prepared by Technical Committee ISO/TC 98, Bases for design of structures, Subcommittee
SC 3, Loads, forces and other actions.
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ISO 21650:2007(E)
Introduction
This International Standard, which deals with the actions from waves and currents on structures in the coastal
zone and in estuaries, is the first of its kind. Waves and currents and actions from waves and currents on
structures in deeper water, especially structures for the petroleum industry, are dealt with in ISO 19901-1 and
ISO 19902, ISO 19903 and ISO 19904-1. Some of the structural elements for deeper water structures and
coastal structures are the same, especially elements with cylindrical shapes. There will thus be, to some
extent, an overlap between this International Standard and other ISO standards on the wave and current
actions on cylindrical structural elements. There is though, a difference in wave conditions and wave
kinematics between coastal waves and deeper water waves.
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INTERNATIONAL STANDARD ISO 21650:2007(E)
Actions from waves and currents on coastal structures
1 Scope
This International Standard describes the principles of determining the wave and current actions on structures
of the following types in the coastal zone and estuaries:
⎯ breakwaters:
⎯ rubble mound breakwaters;
⎯ vertical and composite breakwaters;
⎯ wave screens;
⎯ floating breakwaters;
⎯ coastal dykes;
⎯ seawalls;
⎯ cylindrical structures (jetties, dolphins, lighthouses, pipelines etc.).
For the rubble mound structures it is not possible to determine the forces on and the stability of each individual
armour unit because of the complex flow around and between each armour unit. But there are formulae and
principles to estimate the necessary armour unit mass given the design wave conditions. Coefficients in these
formulae are based on hydraulic model tests. Since the rubble mound structures are heavily used, they are
included in this International Standard, although they may not be treated exactly in accordance with ISO 2394.
This International Standard does not include breakwater layout for harbours, layout of structures to manage
sediment transport, scour and beach stability or the response of flexible dynamic structures, except vortex
induced vibrations.
Design will be performed at different levels of detail:
⎯ concepts;
⎯ feasibility;
⎯ detailed design.
This International Standard is aimed at serving the detailed design.
It is pointed out that the annexes are only informative and are not guidelines/manuals. The annexes have no
regulatory power.
Wave and current conditions vary for different construction sites. It is very important to assess the wave and
current conditions at a given site. Assessment procedures for these conditions and for their uncertainties are
included.
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ISO 21650:2007(E)
2 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
2.1
actions
force (load) applied to the structure by waves and/or currents
2.2
anchors
units placed on the seabed, such as ship anchors, piles driven into the seabed or concrete blocks, to which
mooring lines are attached to restrain a floating object from excessive movements
2.3
annual maximum method
method of estimating extreme wave heights based on a sample of annual maximum wave heights
2.4
armour layer
protective layer on a breakwater, seawall or other rubble mound structures composed of armour units
2.5
armour unit
relatively large quarry stone or concrete shaped unit that is selected to fit specified geometric characteristics
and density
2.6
astronomical tide
phenomenon of the alternate rising and falling of sea surface solely governed by the astronomical conditions
of the sun and the moon, which is predicted with the tidal constituents determined from harmonic analysis of
tide level readings over a long period
2.7
breakwater
structure protecting a shore area, harbour, anchorage and/or basin from waves
2.8
buoyancy
resultant of upward forces, exerted by the water on a submerged or floating body, equal to the weight of the
water displaced by this body
2.9
chart datum
CD
reference level for soundings in navigation charts
2.10
core
inner portion of a breakwater, dyke and rubble mound structures, often with low permeability
2.11
crest
1. highest point of a coastal structure
2. highest point of a wave profile
2.12
crown wall
concrete superstructure on a rubble mound
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ISO 21650:2007(E)
2.13
datum level
reference level for survey, design, construction and maintenance of coastal and maritime structures, often set
at a chart datum or national geodetic datum
2.14
deep water
water of such a depth that surface waves are little affected by bottom topography, being larger than about
one-half the wavelength
2.15
design water level
DWL
water level selected for functional design, structural design and stability analysis of marine structures
NOTE Generally it is the water level that mostly affects the safety of the structures/facilities in question. DWL is
chosen in view of the acceptable level of risk of failure/damage.
2.16
density driven currents
currents induced by horizontal gradients of water density generated by changes in the salinity and/or
temperature, which are caused by the influx of fresh water from run-off from land through an estuary, heat flux
from coastal power stations, or other reasons
2.17
diffractions coefficient
ratio of the height of diffracted waves to the height of incident waves
2.18
directional spreading function
function expressing the relative distribution of wave energy in the directional domain
2.19
directional wave spectrum
function expressing the energy density distribution of waves in the frequency and directional domains, being
expressed as the product of frequency wave spectrum and the directional spreading function
2.20
drag coefficient
coefficient used in the Morison equation to determine the drag force
2.21
dyke berms
nearly horizontal area in the seaward and landward dyke slope which are primarily built to provide access for
maintenance and amenity and which reduce wave run-up and overtopping
2.22
dyke toe
part of a dyke that terminates the base of the dyke on its seaward face
NOTE Various toe constructions are used to prevent undermining of the dyke.
2.23
extreme sea state
extreme waves
state of waves occurring a few dozen times a year to once in many years, expressed with the significant wave
height and the mean or significant wave period at the peak of storm event
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ISO 21650:2007(E)
2.24
filter
intermediate layer, preventing fine materials of an underlayer from being washed through the voids of an
upper layer
2.25
floating breakwater
moored floating object to reduce wave heights in the area behind the floating breakwater
2.26
foreshore
shallow water zone near the shore on which coastal dykes, seawalls and other structures are built
NOTE In beach morphology the term foreshore is used to denote the part of the shore lying between the crest of the
seaward berm and the ordinary low water mark.
2.27
frequency wave spectrum
function expressing the energy density distribution of waves in the frequency domain
2.28
geotextile
synthetic fabric which may be woven or non-woven used as a filter
2.29
highest astronomical tide
HAT
tide at the highest level that can be predicted to occur under average meteorological conditions and under any
combination of astronomical conditions
NOTE HAT is not reached every year and does not represent the highest sea level that can be reached, because
storm surges and tsunamis may cause considerably higher levels to occur.
2.30
highest wave height
height of the highest wave of a given wave record or that in a wave train under a given sea state
2.31
impulsive wave pressure
water pressure of high peak intensity with a very short duration induced by the collision of the front surface of
a breaking wave with a structure or the collision of a rising wave surface with a horizontal or slightly inclined
deck of a pier
2.32
inertia coefficient
coefficient used in the Morison equation to determine the inertia force
2.33
international marine chart datum
IMCD
chart datum set at the lowest astronomical tide level, as adopted by the International Hydrographic
Organization (IHO)
2.34
jetty GB
pier US
deck structure supported by vertical and possibly inclined piles extending into the sea, frequently in a direction
normal to the coastline
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ISO 21650:2007(E)
2.35
lift coefficient
coefficient used to determine the lift force
2.36
lowest astronomical tide
LAT
tide at the lowest level that can be predicted to occur under average meteorological conditions and under any
combination of astronomical conditions
NOTE LAT is not reached every year and does not represent the lowest sea level which can be reached, because
storm surges (negative) and tsunamis may cause considerably lower levels to occur.
2.37
mean high water springs
MHWS
average height of high waters, occurring at the time of spring tides
2.38
mean low water springs
MLWS
average height of low waters occurring at the time of the spring tides
2.39
mean sea level
MSL
average height of the sea level for all stages of the tide over a 19-year period, generally determined from
hourly height readings
2.40
mean water level
MWL
average elevation of the water surface over a given time period, usually determined from hourly tidal level
readings
NOTE The monthly mean water level varies around seasons by a few tens of centimetres.
2.41
mean wave period
average period of all waves among a given wave record
NOTE The mean wave period is often estimated from the spectral information obtained from a wave record.
See 5.2.1.
2.42
moorings
ropes, wires or chains to hold a floating object in position
2.43
overtopping
passing of water over the top of a structure as a result of wave run-up or surge actions
NOTE This definition could serve as a general definition and should not be given individually for each structure.
2.44
parapet
low wall built along the crest of a seawall
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2.45
peaks-over-threshold method
POT method
method of estimating extreme wave heights based on a sample of peak heights of storm waves exceeding
some threshold level
2.46
peak wave period
period corresponding to the peak of frequency wave spectrum
2.47
permeability
capacity of bulk material (sand, crushed rock, soft rock in situ) in permitting movement of water through its
pores
2.48
pipeline
structure for carrying water, oil, gas, sewage, etc.
2.49
piping
erosion of closed flow channels caused by water flowing through soil usually underneath the dyke body
NOTE Soil particles are carried about by seepage flow, thus endangering the stability of the dyke.
2.50
pore pressure
interstitial pressure of water within a mass of soil or rock
2.51
porosity
percentage of the total volume of a soil and/or granular material occupied by air/gas and water
2.52
pulsating wave pressure
wave pressure with a period comparable with the wave period
2.53
refraction coefficient
ratio of the height of waves having been affected by the refraction effect in shallow water to their height in
deep water with the shoaling effect eliminated
2.54
reflection coefficient
ratio of the height of reflected waves to the height of incident waves
2.55
revetment
cladding of concrete slabs, asphalt, clay, grass and other materials to protect the surface of a sea dyke
against erosion
2.56
rip-rap
usually, well-graded quarry stone, randomly placed as an armour layer to prevent erosion
2.57
rock
aggregate of one or more minerals
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ISO 21650:2007(E)
2.58
run-up/run-down
phenomenon of waves running up and down the seaward slope of a sloping structure, their height being
measured as the vertical distance from the still water level
2.59
R-year wave height
extreme wave height corresponding to the return period of R years
NOTE When used, the specific value of R is indicated such as 100-year wave height.
2.60
scour
removal of underwater sand and stone material by waves and currents, especially at the base or toe of a
structure
2.61
sea state
condition of sea surface within a short time span, being expressed with characteristic wave heights, periods
and directions
2.62
seaward dyke slope
slope of the dyke on the seaward side that is generally flatter than 1:4 to reduce wave run-up, protected by a
revetment made of clay and grass, concrete slabs, asphalt, or stones to prevent erosion
2.63
shallow water
water of such a depth that surface waves are noticeably affected by bottom topography, being less than about
one-half the wavelength
NOTE Region of water in which waves propagate is sometimes classified into three categories of deep water,
intermediate depth, and shallow water. According to this classification, shallow water represents the zone of depth less
than about one-twentieth of the wavelength.
2.64
shoaling coefficient
ratio of the height of waves affected by the depth change in shallow water to their height in deep water with
the refraction effect eliminated
2.65
shoreward dyke slope
slope of dyke on the landward side, generally no steeper than 1:3 to prevent erosion by wave overtopping
NOTE It is generally protected by a revetment made of clay/grass.
2.66
significant wave height
average height of the one-third highest waves of a given wave record
NOTE The significant wave height is often estimated from the spectral information obtained from a wave record.
See 5.2.1.
2.67
significant wave period
average period of the one-third highest waves of a given wave record
2.68
slamming actions
actions when a water surface and a structure suddenly collide
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ISO 21650:2007(E)
2.69
still water level
SWL
level of water surface in the absence of any wave and wind actions, is also called the undisturbed water level
2.70
stone
quarried or artificially broken rock for use in construction, either as an aggregate or cut into shaped blocks as
dimension stone
2.71
storm surge
phenomenon of the rise of the sea surface above astronomical water level on the open coast, bays and on
estuaries due to the action of wind stresses on the water surface, the atmospheric pressure reduction, storm-
induced seiches, wave set-up and others
2.72
swell
wind-generated waves that have advanced out of the wave generating area and are no longer affected by
winds
2.73
tidal currents
alternative or circulating currents associated with tidal variation
NOTE Tides and tidal currents are generally strongly modified by the coastline.
2.74
toe
lowest part of sea- and port-side breakwater slope, generally forming the transition to the seabed
2.75
total sample method
method of estimating extreme wave heights by extrapolating a distribution of all the wave heights measured at
a site of interest
2.76
tsunami
long waves with the period of several minutes to one hour and the height up to a few tens of meters, which are
generated by the vertical movement of sea floor associated with a submarine earthquake, by plunging of large
mass of earth into water by land slide or volcanic eruption, and other causes
2.77
uplift
upward water pressure exerted up the base of a structure or pavement due to waves, excluding buoyancy
2.78
vortex induced vibration
VIV
vibration induced by vortexes shed alternatively from either side of a cylinder in a current and/or waves
2.79
wave climate
description of wave conditions at a particular location over months, seasons or years, usually expressed by
the statistics of significant wave height, mean or significant wave period, and wave direction
2.80
wave induced currents
currents in the nearshore zone, which are induced by the horizontal gradient of wave energy flux being
attenuated by wave breaking
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ISO 21650:2007(E)
2.81
wave pressure
water pressure exerted on a structure induced by the action of waves, excluding hydrostatic pressure
2.82
wave set-up
rise of water level near the shoreline associated with wave decay by breaking
NOTE Wave set-up may amount to more than 10 % of the offshore significant wave height.
2.83
wave transmission coefficient
ratio of the height of waves transmitted behind a structure to the height of incident waves
2.84
wind waves
waves generated by and/or developed by wind
2.85
wind driven current
currents induced by the wind stress on the sea surface
NOTE In coastal waters, wind driven currents are influenced by the bottom topography and the presence of the
coastline.
2.86
wind set-up
rise of water level at the leeward side of a water body caused by wind stresses on the water surface
3 Symbols
H significant wave height or the average height of highest one-third waves
1/3
H highest wave height
max
H significant wave height estimated from wave spectrum
m0
m n-th moment of wave spectrum such as m and m
n 0 2
T significant wave period
1/3
T mean wave period
m
T mean wave period estimated from the zero-th and second moments of wave spectrum
m0,2
T period corresponding to the peak of frequency wave spectrum
p
4 Basic variables for actions from waves and currents
4.1 Water levels
4.1.1 Tides
The astronomical tide levels at a design site shall be calculated with the tidal constituents obtained through
the harmonic analysis of a long-term tide record at the site or those estimated from a nearby tide station.
The highest and lowest water levels that have occurred at or near the site should be taken into account in the
evaluation of the actions from waves and currents.
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ISO 21650:2007(E)
The datum level for maritime structures shall be established with reference to the International Marine Chart
Datum and/or the national geodetic datum levels.
4.1.2 Storm surges and tsunamis
The characteristics of storm surges at a design site should be duly investigated and be taken into
consideration in evaluation of the action of waves and currents.
Investigation of storm surges may include data collection and hindcasting of storm surges in the past, and
numerical evaluation of hypothetical storm surges in the future.
Sets of storm surge water levels and/or storm tides should statistically be analysed for extreme distribution
functions so as to determine R-year storm surge levels.
In the locality where the action of a tsunami is not negligible, tsunami characteristics at the site should be duly
investigated by means of data collection and hindcasting of tsunamis in the past, and/or numerical evaluation
of hypothetical tsunamis in the future.
4.1.3 Joint probability of waves and high water level
Evaluation of the action of waves should be made with due consideration for the joint probability of wave
height and water level, especially at a site where the water is relatively shallow and breaker heights are
controlled by the depth of water under influence of the tide.
The wave measurement data obtained at the location where the largest wave height is limited by the water
depth should not be used for extreme statistical analysis for the estimation of storm wave conditions at the
water deeper than the site of measurements.
4.2 Waves
4.2.1 Wave heights and periods
The characteristic heights of wind waves and swell for evaluation of the action of waves should be the
significant wave height H and the highest wave height H , which are defined by the zero-crossing method
1/3 max
in the time domain analysis. Other definitions of wave heights may be used as the characteristic wave heights
when a method of evaluation requires the use of such wave heights. The significant wave height may be
1/2
estimated from the zero-th moment of wave spectrum, m , as being equal to 4,0 m . When this estimation is
0 0
employed, the symbol Hm should be used instead of H so as to clarify the estimation method of the
0 1/3
significant wave height, because they may differ by several percent or more (see B.1.2).
The characteristic periods of wind waves and swell for evaluation of the action of waves are the significant
wave period T and the mean period T , which are defined by the zero-crossing method in the time domain
1/3 m
analysis, and the spectral peak period T , which is obtained from the frequency-domain analysis. The mean
p
period may be estimated from the zero-th and second moments of wave spectrum as being equal to
1/2
(m /m ) . When this estimation is employed, the symbol T should be used so as to clarify the estimation
0 2 m0,2
method of the mean wave period, because the spectrally estimated mean period is generally smaller than the
individually counted mean period.
Because of the random nature of wind waves and swell, the heights and periods of individual waves in a given
sea state are distributed over broad ranges of variation. Statistical distributions of individual wave heights and
periods should be taken into consideration when evaluating actions from waves in shallow water (see B.1).
4.2.2 Wave spectrum
Characteristics of wind waves and swell may also be represented with the directional wave
...
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