1
Report for Installation of LiDar based Offshore Structure for wind
measurement
Submitted
to
Ministry of Environment and Forest
Government of India
Delhi – 110003
By
SAMIRAN UDAIPUR WINDFARMS LIMITED
Ahmedabad
Technical Consultant
National Institute of Ocean Technology
Ministry of Earth Sciences, Govt. of India
Chennai -600 100 February 2016
2
Table of Contents Table of Figures ......................................................................................................................... 4
List of Tables ............................................................................................................................. 4
1. Form 1 ................................................................................................................................ 5
2. Executive summary .......................................................................................................... 21
3. Introduction ...................................................................................................................... 21
3.1. Need for Renewable Energy & World Scenario ....................................................... 21
3.2. Offshore Wind Potential in India and wind energy Policy ....................................... 22
3.3. SUWL, SEL and NIOT involvement ........................................................................ 24
4. Project Description........................................................................................................... 24
4.1. Site Details ................................................................................................................ 24
4.2. Bathymetry & Physical Processes ............................................................................. 25
4.2.1. Bathymetry ......................................................................................................... 25
4.2.2. Tide .................................................................................................................... 25
4.2.3. Currents .............................................................................................................. 26
4.2.4. Wave .................................................................................................................. 26
4.2.5. Rainfall ............................................................................................................... 26
5. Proposed Data collection Mast ........................................................................................ 26
5.1. Description with layout ............................................................................................. 26
5.2. Structural Design ....................................................................................................... 27
4.2.1. Basic Load ................................................................................................................. 27
5.2.1.1. Dead load........................................................................................................ 27
5.2.1.2. Live Load ....................................................................................................... 28
5.2.1.3. Wind loads...................................................................................................... 28
5.2.1.4. Hydrodynamic loads ...................................................................................... 28
5.2.1.5. Seismic loads .................................................................................................. 30
5.2.2. Load Combinations................................................................................................ 32
5.2.3. Monopile ................................................................................................................ 32
5.2.4. Cyclones ................................................................................................................ 33
5.2.4.1. Axial Compression: ............................................................................................ 34
5.2.4.2. Elastic Local Buckling Stress ............................................................................. 34
3
5.2.4.3. Inelastic local buckling Stress. ............................................................................ 34
5.2.4.4. Allowable Bending Stress: .................................................................................. 36
5.2.5. Earth Quake ............................................................................................................... 36
5.2.5.1. Member Capacity for Earthquake Load Combination: ....................................... 37
5.2.6. Boat Impact ................................................................................................................ 37
5.2.6.1. Member Capacity for Boat Impact Combination: .............................................. 37
5.2.7. Platform...................................................................................................................... 38
5.2.7.1. Material Properties .............................................................................................. 38
5.2.7.2. Loads & Load combinations ............................................................................... 39
5.2.7.3. Staad Results ....................................................................................................... 40
5.2.7.4. Sectional Classification ....................................................................................... 41
5.2.7.5. Shear Capacity .................................................................................................... 41
5.2.7.6. Moment Capacity ................................................................................................ 42
5.2.7.7. Check for deflections .......................................................................................... 42
5.2.7.8. Check for web buckling ...................................................................................... 42
5.2.7.9. Check for web bearing ........................................................................................ 43
5.2.7.10. Check for stiffeners ........................................................................................... 43
5.2.7.11. Check for compression flange buckling ........................................................... 43
5.2.7.12. Secondary beams .............................................................................................. 44
5.2.7.13. Sectional Classification ..................................................................................... 44
5.2.7.14. Shear Capacity .................................................................................................. 44
5.2.7.15. Moment Capacity .............................................................................................. 45
5.2.7.16. Check for deflections ........................................................................................ 45
5.2.8.17. Check for web buckling .................................................................................... 46
5.2.7.18. Check for web bearing ...................................................................................... 46
5.2.7.19. Check for stiffeners ........................................................................................... 46
5.2.7.20. Check for compression flange buckling ........................................................... 47
5.2.7.21. Welded Connection design ............................................................................... 47
4
6. Installation procedure....................................................................................................... 48
6.1. Decommissioning procedure ..................................................................................... 49
6.2. Construction and operational impact assessment ...................................................... 50
6.2.1. Noise level ......................................................................................................... 50
6.2.2. Air Environment ................................................................................................ 50
6.2.3. Water Environment ............................................................................................ 50
6.2.4. Fishery................................................................................................................ 50
7. Project Schedule and cost estimates ................................................................................ 51
7.1 Project Schedule......................................................................................................... 51
7.2 Cost estimate .............................................................................................................. 51
Table of Figures
s
Fig. 1 Installed Cumulative Capacity in European countries (Source: EWEA, (2013)) ......... 22
Fig. 2 Wind Speed Distribution at 80m Elevation ................................................................... 23
Fig. 3 Power Production for 3 MW Offshore Wind Turbine. .................................................. 23
Fig. 4 Google earth map –Jakhau ............................................................................................ 23
Fig. 5 Topography map(20km buffer)-Jakhau ......................................................................... 23
Fig. 6 Regional Connectivity map-Jakhau .............................................................................. 23
Fig. 7 Topography map-Jakhau ............................................................................................... 23
Fig. 8 Hydrographic map-Jakhau ............................................................................................. 23
Fig. 9 Bathymetry profile for the prosed site ........................................................................... 25
Fig. 10 Layout of Supporting Platform for LiDar.................................................................... 27
Fig. 11 Current profile for operational and critical condition .................................................. 28
Fig. 12 Regions of Applicability of Various Wave Theories .................................................. 30
Fig. 13 Seismic zone of India .................................................................................................. 31
Fig. 14 Acceleration Spectrum ............................................................................................... 32
Fig. 15 Deflected Profiles for Various Sea States .................................................................... 33
Fig. 16 Installation methodology for wind mast ...................................................................... 49
List of Tables
Table 1 Instruments for collecting various Parameters............................................................ 26
Table 2 Waves Parameters ....................................................................................................... 29
Table 3 Soil Parameters for Different Layers .......................................................................... 33
5
1. Form 1
(For seeking clearance for project attracting CRZ notification)
Name of the project: Installation of Lidar based Offshore structure for wind
measurement
CRZ classification of the
area:
CRZ-IV
Expected cost of the
project:
4 crore
(I) Basic Information
Sr
No. Item Details
1. Name of the project/s
Installation of Lidar based Offshore
structure for wind measurement in
Jakhau
2. S. No. in the schedule
3.
Proposed capacity/area/length/tonnage to
be handled/command area/lease
area/number of wells to be drilled
1.2m diameter monopile to support
5m diameter platform which is
located at 7.5m clearance above
water level
4. New/Expansion/Modernization New
5. Existing Capacity/Area etc. Not Applicable
6. Category of Project i.e. ‘A’ or ‘B’ B1
7. Does it attract the general condition? If
yes, please specify.
No
8. Does it attract the specific condition? If
yes, please specify.
No
9. Location:
N23o 07’ 24.42” E 68o 27’ 48.24”
Plot/Survey/Khasra No. NA
Village Jakhau
Tehsil Abdasa
6
Sr
No. Item Details
District Kutch
State Gujarat
10. Nearest railway station/airport along with
distance in km
Naliya (28km from Jakhau).
Bhuj (120km from Jakhau)
11. Nearest Town, city, District Headquarters
along with distance in km.
Naliya is the district headquarters
located 28km away from this
location
12.
Village Panchayats, Zilla Parishad,
Municipal Corporation, Local body
(complete postal addresses with
telephone nos. to be given)
Offshore facility near Jakhau port.
13. Name of the applicant Samiran Udaipur Windfarms Limited
14. Registered Address
C/o Suzlon Energy Limited
Suzlon House,
5,Shrimali Society,
Near Sri Krishna Complex
Navrangpura,Ahmedabad-380009
Gujarat
India
15. Address for correspondence :
Name Mr. Ranjit Singh Parmar
Designation (Owner/Partner/CEO) Sr. President-India Business
Address
C/o Suzlon Energy Limited
Suzlon House,
5,Shrimali Society,
Near Sri Krishna Complex
Navrangpura,Ahmedabad-380009
7
Sr
No. Item Details
Gujarat
India
Pin Code 380009
E-mail [email protected]
Telephone No. 079-66045201, 66045000
Fax No. 079-26565540, 26442844
16.
Details of Alternative Sites examined, if
any. Location of these sites should be
shown on a topo sheet
NA
17. Interlinked Projects None
18. Whether separate application of
interlinked project has been submitted?
NA
19. If yes, date of submission -
20. If no, reason -
21.
Whether the proposal involves
approval/clearance under: if yes, details
of the same and their status to be given.
( c )
(a) The Forest (Conservation) Act, 1980?
(b) The Wildlife (Protection) Act, 1972?
(c) The C.R.Z Notification, 1991?
22. Whether there is any Government
Order/Policy relevant/relating to the site?
Offshore wind energy policy of
Ministry New and Renewable Energy
23. Forest land involved (hectares) None
24.
Whether there is any litigation pending
against the project and/or land in which
the project is propose to be set up?
None
(a) Name of the Court
(b) Case No.
(c) Orders/directions of the Court, if any None
8
Sr
No. Item Details
and its relevance with the proposed
project.
(II) Activity
1. Construction, operation or decommissioning of the project involving
actions which will cause physical changes in the locality (topography,
land use, changes in water bodies and the like)
S.No Information/Check list
confirmation
Yes/
No
1.1 Permanent or temporary
change in land use, land cover
or topography including
increase in intensity of land use
(with respect to local land use
plan)
No The proposed site is 18km from the shore
and hence there is no change in the land
use
1.2 Details of CRZ classification as
per the approved Coastal Zone
Management Plan?
CRZ IV as per CRZ notification 2011
1.3 Whether located in CRZ -1
area?
No Not Applicable.
1.4 The distance from the CRZ – I
areas?
- 16.3km
1.5 Whether located within the
hazard zone as mapped by
Ministry of Environment &
Forests/National Disaster
Management Authority?
No Not Applicable.
1.6 Whether the area is prone to
cyclone, tsunami, tidal surge,
subduction, earth quake etc.?
Yes Extreme conditions such as cyclone and
earthquake are being considered in
structural design of the Wind Mast.
9
S.No Information/Check list
confirmation
Yes/
No
1.7 Whether the area is prone for
salt water ingress?
No Not Applicable.
1.8 Clearance of existing land,
vegetation & buildings?
No Not Applicable.
1.9 Creation of new land uses? No Not Applicable
1.10 Pre-construction investigations
e.g., borehole, soil testing?
No Not Applicable
1.11
Construction works Yes Pile driving and erection of structure.
1.12 Demolition works? No Not Applicable
1.13 Temporary site used for
construction works or housing
of construction workers?
No Not Applicable
1.14 Above ground buildings,
structures or earth works
including linear structures, cut
and fill or excavations
No Not Applicable
1.15 Underground works including
mining or tunneling?
No Not Applicable
1.16 Reclamation works? No Not Applicable
1.17 Dredging/ reclamation/land
filling/disposal of dredged
material etc?
No Not Applicable
1.18 Off shore structures? Yes Offshore wind mast (1.2m diameter pile to
support 5m diameter platform which is
located at 10m above MSL.
1.19 Production and manufacturing
processes?
No Not Applicable
10
S.No Information/Check list
confirmation
Yes/
No
1.20 Facilities for storage of goods
or materials?
No Not Applicable
1.21 Facilities for treatment or
disposal of solid waste or liquid
effluent?
No Not Applicable
1.22 Facilities for long term housing
of operational workers?
No Not Applicable
1.23 New road, rail or sea traffic
during construction or
operation?
No
Not Applicable
1.24 New road, rail, air water borne
or other transport infrastructure
including new or altered routes
and stations, ports, airports
etc?
No The route is away from the navigation and
hence no alteration for routes required.
1.25 Closure or diversion of existing
transport routes or
infrastructure leading to
changes in traffic movements?
No Not Applicable
1.26 New or diverted transmission
lines or pipelines?
No Not Applicable
1.27 Impoundment damming,
culverting, realignment or other
changes to the hydrology of
water courses or aquifers?
No Not Applicable
1.28 Stream and river crossings? No Not Applicable
1.29 Abstraction or transfers of
water from ground or surface
waters?
No Not Applicable
1.30 Changes in water bodies or the No Not Applicable
11
S.No Information/Check list
confirmation
Yes/
No
land surface affecting drainage
or run-off?
1.31 Transport of personnel or
materials for construction,
operation or decommissioning?
Yes Transport of personnel or materials for
construction, operation or decommissioning
through vessel (boat / Jackup / barge).
1.32 Long-term dismantling or
decommissioning or restoration
works?
No No dismantling or decommissioning is
proposed.
1.33 Ongoing activity during
decommissioning which could
have an impact on the
environment?
No Not envisaged
1.34 Influx of people to an area in
either temporarily or
permanently?
Yes Temporary construction workers during
construction phase.
Operational / maintenance staff will do
monthly visit to the platform.
1.35 Introduction of alien species? No Not Applicable
1.36 Loss of native species or
genetic diversity?
No Not Applicable
1.37 Any other actions? No Not Applicable
2. Use of natural resources for construction or operation of the project
(such as land, water, materials or energy, especially any resources
which are non-renewable or in short supply):
S.No Information/Check list
confirmation
Yes/
No
Details thereof (with approximate
quantities/rates, wherever possible)
with source of information data
2.1 Land especially undeveloped No Not Applicable
12
S.No Information/Check list
confirmation
Yes/
No
Details thereof (with approximate
quantities/rates, wherever possible)
with source of information data
or agricultural land (ha)
2.2 Water (expected source &
competing users) unit: KLD
No Not Applicable
2.3 Minerals (MT) No Not Applicable
2.4 Construction material – stone,
aggregates, sand/soil
(expected source – MT)
No Only prefabricated steel will be used..
2.5 Forest and timber (source –
MT)
No Not Applicable
2.6 Energy including electricity
and fuels (source, competing
users) Unit: fuel (MT), energy
(MW)
No Self-propelled boats are being used.
2.7 Any other natural resources
(use appropriate standard
units)
No Not Applicable
3. Use, storage, transport, handling or production of substances or
materials, which could be harmful to human health or the environment
or raise concerns about actual or perceived risks to human health
S.N
o
Information/Check list
confirmation
Yes/
No
Details thereof (with approximate
quantities/rates, wherever possible)
with source of information data
3.1 Use of substances or materials,
which are hazardous (as per
MSIHC rules) to human health or
the environment (flora,fauna and
water supplies)
No Not Applicable
3.2 Changes in occurrence of No Not Applicable
13
S.N
o
Information/Check list
confirmation
Yes/
No
Details thereof (with approximate
quantities/rates, wherever possible)
with source of information data
disease or affect disease vectors
(e.g., insect or water borne
diseases)
3.3 Affect the welfare of people e.g.,
by changing living conditions?
No Not Applicable
3.4 Vulnerable groups of people who
could be affected by the project
e.g., hospital patients, children,
the elderly etc.,
No Not Applicable
3.5 Any other causes, that would
affect local communities,
fisherfolk, their livelihood,
dwelling units of traditional local
communities etc
None Not Applicable
4. Production of solid wastes during construction or operation or
decommissioning (MT/month)
S.No Information/Check list
confirmation
Yes /
No
Details thereof (with approximate
quantities/rates, wherever possible) with
source of information data
4.1 Spoil, over burden or mine
wastes
No Not Applicable
4.2 Municipal waste (domestic
and or commercial wastes)
No Not Applicable
4.3 Hazardous wastes (as per
hazardous waste
management rules)
No Not applicable
4.4 Other industrial process
wastes
No Not Applicable
14
S.No Information/Check list
confirmation
Yes /
No
Details thereof (with approximate
quantities/rates, wherever possible) with
source of information data
4.5 Surplus product No Not Applicable
4.6 Sewage sludge or other
sludge from effluent
treatment
No Not Applicable
4.7 Construction or demolition
wastes
No Not Applicable
4.8 Redundant machinery or
equipment
No Not Applicable
4.9 Contaminated soils or other
materials
No Not Applicable
4.10 Agricultural wastes No Not Applicable
4.11 Other solid wastes No Not Applicable
5. Release of pollutants or any hazardous, toxic or noxious substances to
air (Kg/hr)
S.No Information/Check list
confirmation
Yes/
No
Details thereof (with approximate
quantities/rates, wherever possible) with
source of information data
5.1 Emissions from combustion
of fossil fuels from stationary
or mobile sources
No
Not Applicable
5.2 Emissions from production
processes
No Not Applicable
5.3 Emissions from materials
handling including storage or
transport
No Not Applicable
5.4 Emissions from construction No Not Applicable
15
S.No Information/Check list
confirmation
Yes/
No
Details thereof (with approximate
quantities/rates, wherever possible) with
source of information data
activities including plant and
equipment
5.5 Dust or odours from
handling of materials
including construction
materials, sewage and
waste
No Not Applicable
5.6 Emissions from incineration
of waste
No Not Applicable
5.7 Emissions from burning of
waste in open air (e.g., slash
materials, construction
debris)
No Not Applicable
5.8 Emissions from any other
sources
No Not Applicable
6. Generation of noise and vibration and emissions of light and Heat:
S.No Information/Check list
confirmation
Yes/No Details thereof (with approximate
quantities/rates, wherever possible)
with source of information data
6.1 From operation of
equipment e.g., engines,
ventilation plant, crushers
Yes Negligible noise is expected during
operation. The machinery to be used will
be properly maintained to avoid noise
pollution.
6.2 From industrial or similar
processes
No Not Applicable
6.3 From construction or Yes During construction there will be noise
16
S.No Information/Check list
confirmation
Yes/No Details thereof (with approximate
quantities/rates, wherever possible)
with source of information data
demolition arising out of loading/unloading,
transportation of construction materials,
crane operation, piling work, etc which will
not be significant.
Noise levels will be monitored to ensure
compliance to norms.
6.4 From blasting or piling Yes Negligible noise is expected during
construction work which is in the sea.
6.5 From construction or
operational traffic
No Not applicable
6.6 From lighting or cooling
systems
No Not Applicable
6.7 From any other sources None -
7. Risks of contamination of land or water from releases of pollutants into
the ground or into sewers. Surface waters, ground water , coastal waters
or the sea
S.No Information/Check list
confirmation
Yes/No Details thereof (with approximate
quantities/rates, wherever possible)
with source of information data
7.1 From handling, storage, use
or spillage of hazardous
materials
No Not applicable
17
S.No Information/Check list
confirmation
Yes/No Details thereof (with approximate
quantities/rates, wherever possible)
with source of information data
7.2 From discharge of sewage
or other effluents to water or
the land (expected mode
and place of discharge)
No Not applicable
7.3 By deposition of pollutants
emitted to air into the land or
into water
No Not Applicable
7.4 From any other sources No Not Applicable
7.5 Is there a risk of long term
build up of pollutants in the
environment from these
sources?
None Not Applicable
8. Risk of accidents during construction or operation of the project, which
could affect human health or the environment
S.No Information/Check list
confirmation
Yes/No Details thereof (with approximate
quantities/rates, wherever possible)
with source of information data
8.1 From explosions, spillages,
fires etc from storage,
handling, use or production
of hazardous substances
No Not Applicable
8.2 From any other causes No Not Applicable
8.3 Could the project be
affected by natural disasters
causing environmental
damage (e.g., floods,
earthquakes, landslides,
No Not Applicable
18
cloudburst etc)
9. Factors which should be considered (such as consequential
development) which could lead to environmental effects or the potential
for cumulative impacts with other existing or planned activities in the
locality
S.No Information/Check list
confirmation
Yes/No Details thereof (with approximate
quantities/rates, wherever possible)
with source of information data
9.1 Lead to development of
supporting facilities,
ancillary development or
development stimulated by
the project which could have
impact on the environment
e.g.,
Supporting infrastructure
(roads, power supply, waste
or waste water treatment
etc.,)
Housing development,
extractive industries, supply
industries, other
NO Not Applicable
9.2 Lead to after use of the site,
which could have an impact
on the environment
No Not Applicable
9.3 Set a precedent for later
developments
No Not Applicable
9.4 Have cumulative effects due
to proximity to other existing
No Not Applicable
19
S.No Information/Check list
confirmation
Yes/No Details thereof (with approximate
quantities/rates, wherever possible)
with source of information data
or planned projects with
similar effects
III. Environmental Sensitivity:
S.N
o
Areas Name/
Identity
Aerial distance (within 15
km ) proposed project
location boundary)
1 Areas protected under
international conventions,
national or local legislation for
their ecological, landscape,
cultural or other related value
None Not Applicable
2 Areas which are important or
sensitive species for ecological
reasons – wetlands,
watercourses or other water
bodies, coastal zone, biospheres,
mountains, forests
None
3 Areas used by protected,
important or sensitive species of
flora or fauna for breeding,
nesting, foraging, resting, over
wintering, migration
None
4 Inland, coastal, marine or
underground waters
Coastal Marine
waters
5 State, national boundaries No Not Applicable
20
6 Routes or facilities used by the
public for access to recreation or
other tourist, pilgrim areas
No Not Applicable
7 Defense installations No Not Applicable
8 Densely populated or built up
area
No Not Applicable
S.N
o
Areas Name/
Identity
9
Areas occupied by sensitive
man-made land uses (hospitals,
schools, places of worship,
community facilities)
No Not Applicable
10 Areas containing important, high
quality or scarce resources
(ground water resources, surface
resources, forestry, agriculture,
fisheries, tourism , minerals)
No - Not Applicable
11 Areas already subjected to
pollution or environmental
damage (those where existing
legal environmental standards
are exceeded)
No - Not Applicable
12 Areas susceptible to natural
hazard which could cause the
project to present environmental
problems
(earthquakes, subsidence,
landslides, erosion, flooding or
extreme or adverse climatic
conditions)
Yes
Seismic Zone ( V)
21
2. Executive summary
As the onshore wind energy demands more space, higher wind speed and visual intrusion the
focus has been shifted towards Offshore Wind Energy in India. The preliminary studies
indicated two wind potential sites in Gujarat and in Tamilnadu. Hence the Government has
announced National Offshore Wind Energy Policy as an initial step towards the development
of offshore wind in the country. This policy allows various government and interested private
agencies to get involved in preliminary data assessments in the potential sites.
Hence Samiran Udaipur Windfarms Limited (SUWL) have entrusted Suzlon Energy Ltd
(SEL) to arrange for the Survey and Investigations off the coast of Jakhau. M/s Suzlon
Energy Limited approached ESSO-NIOT in order to set up a data collecting platform at off
coast Jakhau, Gujarat for a period of two years. M/s SEL along with NIOT has done
preliminary wind assessment, Environmental Impact Assessments and various other
feasibility studies. This report presents the summary of these studies, seeking for CRZ
Clearance from Ministry of Environment, Forest and Climate Change.
3. Introduction
3.1. Need for Renewable Energy & World Scenario
Worldwide, wind energy is accepted as one of the most developed, cost-effective and proven
renewable energy technologies to meet increasing electricity demands in a sustainable
manner. While onshore wind energy technologies have reached a stage of large scale
deployment and have become competitive with fossil fuel based electricity generation with
supportive policy regimes across the world, exploitation of offshore wind energy is yet to
reach a comparable scale. The promising factors for offshore wind development are i) Strong
/ Consistent winds compared to land, ii) Less sound pollution and visual intrusion, iii) Best
benefit to coastal areas due to less transmission cost and iv) Exploitation of available onshore
wind sites.
The first offshore wind power test facility was setup in Sweden, in 1990; however the first
commercial offshore wind farm was commissioned in1991in Denmark [Nikolaou, (2004)].
As of January, 2013 the installed capacities of wind farms in Europe, China and Japan are 5
GW, 0.51 GW and 0.033 GW respectively [EWEA, (2013)]. Proposals exist to expand the
respective capacities to 40 GW (Europe) [EWEA, (2009)], 30 GW (China) [Da et al., 2011]
22
and 1 GW (Japan) [www.ewea.org] by 2020. Actually, more than 90% of the global offshore
wind farms were located in European waters and the contribution from various counties is
shown in Fig. 1. Recently, World’s largest wind farm ‘London Array’ with a capacity of 630
MW is commissioned in United Kingdom [London Array, (2013)]. A project with 0.468 GW
capacity is under construction in USA with proposals for expanding the capacity to 10 GW
by 2020 [U.S. Department of Energy, (2011)].
Fig. 1 Installed Cumulative Capacity in European countries (Source: EWEA, (2013))
3.2. Offshore Wind Potential in India and wind energy Policy
India has achieved significant success in the onshore wind power development with about 24
GW of wind energy capacity already installed and generating power.
The share of the renewable energy sources under operation in India is around 12% [CEA,
(2013)], of its total production, whereas the developed countries already achieved over 20-
30%. Preliminary studies indicated many potential sites in India for wind farms and still this
huge potential remains untapped.
Initial preliminary wind potential studies have been carried out along the Indian coast based
on the available satellite and buoy data. It is observed that the offshore wind of magnitude
6m/s or more persist for more than 300 days along the coast of Tamilnadu and Gujarat. A
suitability analysis for three potential sites of Rameshwaram, Kanyakumari and Jakhau along
the Indian coast was carried out in this study based on the long term wind data (1999 to 2009)
obtained from ESSO - INCOIS. The data obtained at 10m elevation for 10 years were scaled
to 80 m elevation (i.e hub height of wind turbine) using power law. The percentage
59%18%
8%
6%
5%3% 1%
UK
Denmark
Belgium
Germany
Netherland
Sweden
Others
23
distribution of these derived wind speeds for the sites Jakhau, Rameshwaram and
Kanyakumari are shown in Fig. 2. The mean wind speeds at Rameshwaram, Kanyakumari
and Jakhau for derived winds at 80m elevation are 8.5 m/s, 9.1 m/s and 7.3 m/s respectively.
Fig. 2 Wind Speed Distribution at 80m Elevation
Offshore winds were used to estimate the power production from the power curves provided
by the manufacturer. The Plant Load Factor (Ratio of average power produced to the
Capacity of turbine) was estimated for various wind turbines with capacities varying from 1.5
to 5 MW. It was observed that 3.0 MW turbine operates at high Plant Load Factor at all the 3
locations along Indian coast. Fig. 3 shows the power produced along with plant load factors
for the 3 MW turbines, which is optimum for Indian wind conditions, however, which needs
confirmation from the measured data.
Fig. 3 Power Production for 3 MW Offshore Wind Turbine. Fig. 4 Google earth map –Jakhau
Fig. 5 Topography map(20km buffer)-Jakhau
Fig. 6 Regional Connectivity map-Jakhau Fig. 7 Topography map-Jahau
Fig. 8 Hydrographic map-Jahau
Based on these studies Ministry of New and Renewable Energy(MNRE) has formulated
National Offshore Wind Energy Policy in September 2015(Refer Annexure II) attempting to
Per
cen
tag
e o
f D
ay
s
Jakhau Rameshwaram Kanyakumari
24
replicate the success of onshore wind power development in the offshore wind power
development.
Electricity generation from renewable sources of energy is an important element in the
Government’s National Action Plan on Climate Change (NAPCC) announced in the year
2008. With introduction of this policy, the Government of India is committed to provide a
conducive environment for harnessing offshore wind energy in India.
3.3. SUWL, SEL and NIOT involvement
National Wind energy Policy of India provides permission for Carrying out preliminary wind
resource assessment, oceanography & bathymetric surveys etc. by any government agencies
or by interested private players who have proven expertise in offshore studies. While SUEL
is given permission for survey and Investigation offshe coast of Jakhau by the Gujarat
Maritime Board (GMB), (Ref Annexure I) M/s Suzlon Energy Limited on behalf of SUWL
approached ESSO-NIOT for the activities of offshore structures for the wind farms in India. M/s
SEL has requested NIOT to take up the activity of design and installation of LIDAR based
offshore wind mast at offshore location near Jakhau in Gujarat for offshore wind assessment.
M/s SEL with the support of NIOT is setting up a data collecting platform at Jakhau in order
to validate the wind potential sites. This data collection platform will be functioning over a
period of 2-3 years.).
4. Project Description
4.1. Site Details
The project site location is located off coast in kutch district of Gujarat. The project is 18km
from the shore, 30km from Jakhau and 42km from Naliya port. The geographical coordinates
of the site is N23o 07’ 24.42” E68o 27’ 48.24”.The project site location is shown in
Annexure III and Annexure IV. The project site lies within the Indian Territorial waters
which is 12 Nautical miles from baseline. The other major towns near project site are Bhuj,
Kandla and Mundra. Regional connectivity map of the project site is shown in the Annexure
V. Initially three locations have been considered and this location has been finalized based
on suitable soil strata, Hydrodynamic condition and also as it is away from navigation
channel. Other details such as Topographic and Hydrographic are found in Annexure VI and
Annexure VII.
25
4.2. Bathymetry & Physical Processes
4.2.1. Bathymetry
The bathymetry of the project site is relatively flat with minimum undulations. The
bathymetry reveals that from -1 m to -5m contours are almost parallel to the shore. The -5m
contour is at 5.4km from the shore, -10m contour varies from 5.4km to 14.8km away from
the shore. The bathymetry details are shown in Fig.6.The proposed project site is about 10m
from MSL which is shown in Fig.9
Fig. 9 Bathymetry profile for the prosed site
4.2.2. Tide
Mean High higher water level (MHHW): 2.9m
Mean Low higher water level (MLHW): 2.65m
Mean High lower water level (MHLW): 1.43m
Mean Low lower water level (MLLW): 0.63m
26
4.2.3. Currents
The currents in the Gulf and associated Creeks are largely tide induced. Maximum speed of
current is 2m/s.
4.2.4. Wave
Significant wave height, Hs =5.5m
Wave Period, Tp=12s
4.2.5. Rainfall
Average annual rainfall is of 250mm.Generally rainfall occurs in the period of July to
September and the number of wet days per year is 30.
5. Proposed Data collection Mast
5.1. Description with layout
The LIDAR based offshore met mast is to be located at a water depth of 10m with a tidal
variation of 5m. The platform housing LiDAR is at about 7.5m from the MSL. The data
collection platform consists of instruments for collecting various parameters required for
wind potential studies and design of substructure for wind turbine. This data collection
platform is of 5m diameter. The setup of platform is shown in Fig.2 and details of the
instruments are given are given in Table 1. To supply power for operation of these
instruments solar panel and small wind turbines along with battery supply for back are
provided.
S.No Parameters Instrument
1 Wind Velocity, Direction and Profiles LiDar
2 Wave Direction, Height and Periods Wave Rider Buoy
3 Current Velocity, Direction and Profiles ADCP, RCM
4 Tide RTG, ATG
5 PH, Salinity & TSS Water Quality buoy
6 Temperature, Pressure, Humidity Automatic weather Station
Table 1 Instruments for collecting various Parameters
The platform is provided for supporting all the equipment’s required to measure. Platform
consists of central rigid circular beam and main beams radiating from the central beam. Main
27
beams are connected with secondary beams. Trapezoidal plates are resting over the main
beams, over which all equipment loads such as wind turbine, LiDar, solar panels, wind
measurement instruments and batteries are resting.
Fig. 10 Layout of Supporting Platform for LiDar
The Monopole supporting the data collection platform is of 1.2m diameter which is of 25mm
thick. The detailed structural design of the wind mast and platform is as below
5.2. Structural Design
The platform is located at water depth of 10 m with a tidal range 5m. The soil is
predominantly silty sand with an angle of friction as 34o. The maximum current speed at the
location is considered as 1.5m/s.
4.2.1. Basic Load
The various loads considered in the design of support structure include dead load, live load,
wind loads, Hydrodynamic loads and seismic loads.
5.2.1.1. Dead load
Self-weight of the structure, nonstructural members like hand rails, ladder and various
instruments mounted on the platform are considered.
28
5.2.1.2. Live Load
A live load of 5kN/m2 is considered in accordance with IS 875: part-2 to accommodate for
people’s moment during operations and installation of instruments on platform
5.2.1.3. Wind loads
The extreme wind loads were considered in accordance to IS 875 part-3. The critical
(extreme) and operational basic wind speeds at reference height of 10m above SWL were 50
m/s and 12 m/s respectively.
The design wind speed, V = k1 x k2 x k3 x Vb = 53 m/s
Where Vb is Basic wind Speed, k1 is probability factor (risk coefficient), k2 = terrain, height
and structure size factor and k3 = topography factor.
The forces on monopole due to this wind profile were calculated in accordance with API RP
2A WSD.
F= Cs (ρ/2) A V2 = 1.03KN
Where F is wind force, ρ is mass density of air (1.225 kg/m3), V is wind speed, Cs is shape
coefficient (0.5 for cylinder shape) and A is projected area.
5.2.1.4. Hydrodynamic loads
In this study two sea states as shown in Table 2 were considered, critical condition (extreme
environment) and operational condition. In critical condition the maximum wave height was
3m with a period of 12s and for operational condition the maximum wave height was 1.5m
with a period was 7s.The current profiles considered for both sea states are shown in Fig. 2.
Wave and current were considered to act in the same direction.
Fig. 11 Current profile for operational and critical condition
-15
-13
-11
-9
-7
-5
-3
-1
0 0.5 1 1.5 2
Heig
ht
(m)
Velocity (m/s)
Current Profile
Operational
Extreme
29
Sea
State
Wave Height
(H, m)
Wave Period
(T, s)
Water
Depth
(d, m)
Wave Length
(L, m)
H
g T2
d
g T2
Severe 3 12 15 137 0.0021 0.011
Normal 1.5 7 15 68 0.0031 0.031
Table 2 Waves Parameters
Wave kinematics is estimated using suitable wave theory. Fig.6 (API RP 2A WSD, 2007)
shows suitability of various wave theories for a region. Selection of wave theory depends on
wave height, Period and water depth. The required parameters for selecting suitable wave
theory were given in column 6 and 7 of Table 4. Based on these parameters and Fig.6, Stokes
5th order wave theory was considered for calculating wave kinematics.
Wave and Current forces were calculated using Morison’s equation. This was a semi-
empirical formula which assumes the total force as a sum of inertia component due to the
fluid acceleration and a drag component due to fluid velocity. Applicability of Morison’s
equation depends on the ratio of the wavelength to the member diameter. If this ratio was
greater than 5 then the structure will not cause incident wave to diffract and Morison’s
equation can be used. If ratio was less than 5 then Diffraction theory, which computes the
pressure acting on the structure due to both the incident wave and the scattered wave, should
be used, instead of the Morison equation, to determine the wave forces. In this study, this
ratio is more than 5 for waves considered in all stated. So, Morison equation is used for
calculating forces which was of the following form.
F = CD (ρ/2) D V2 + (π/4) D2 ρ Cm U2
Where F is Force per unit length, ρ is mass density of water (1025 kg/m3), CD is Drag
Coefficient for Tubular Section (1.05 – Rough surface), Cm is Inertia Coefficient for Tubular
Section (1.2 – Rough surface), U =Acceleration of water particle, V =Velocity of water
particle.
30
Fig. 12 Regions of Applicability of Various Wave Theories
For each sea state the phase of the wave was varied from 0° to 360° with a step of 10°. It was
observed that maximum base shear and base moment for Monopile occurs at a phase shift of
350°. The wave load at this phase angle was considered for analysis.
5.2.1.5. Seismic loads
Response Spectral method was used for calculating Earthquake forces for both the
substructure concepts. In this method response of a structure was obtained by combining the
responses of different Mode Shapes. Initially, free vibration analysis was carried out to obtain
the modal frequencies and mode shapes. For each mode, a response was obtained from the
design spectrum based on the modal frequency and they were combined using suitable modal
combination rule to provide an estimate of the total response of the structure. Complete
Quadratic Combination (CQC) modal combination rule was used here, as it gives more
reliable values when compared with square root of the sum of the squares (SRSS) and sum of
absolute peaks methods. In this study for earthquake load cases the Pile-Soil iteration was
assumed to be linear.
31
Fig. 13 Seismic zone of India
Earthquake spectrum was considered as per IS 1893 Part–4.The considered site comes in
zone II (Rameswaram).Reduction factor “R” is 2. Importance factor “I” is 1.5 (same as steel
chimney). Soil type is taken as Type II (medium soil). ‘Sa/g’ is the spectral acceleration
coefficient corresponding to site specific spectra. The seismic coefficient was calculated as.
𝐴ℎ =[
𝑍
2]×[
𝑆𝑎𝑔
]
(𝑅
𝐼)
Where Ah is Horizontal acceleration coefficient, Sa/g is the spectral acceleration, Z is Zone
factor (0.36), R is Response Reduction factor (2) and I is Importance Factor (1.5).
The acceleration spectrum shown in Fig.7 was obtained by multiplying Ah with acceleration
due to gravity ‘g’ and Scale Factor. The Scale Factor for spectrum along both horizontal
directions was 1.0 and for vertical direction was 0.5.
32
Fig. 14 Acceleration Spectrum
5.2.2. Load Combinations
Load combinations for offshore wind turbine are considered as per API RP 2A WSD. Three
critical cases were considered in design of support structure. Extreme sea state during critical
like cyclone, LC1. As a design rule occurrence of two critical events should not be
considered at same time in design of any structure. So, while considering earthquake loads all
other environmental loads should be normal condition (i.e. operational condition), LC2.
Impact of boat on structure at controlled condition, LC3 Combinations. As the Monopile was
axi-symmetric, application of load along any direction will have same influence. So, wave
heading is not varied with in each load combination.
5.2.3. Monopile
The support structure is designed for three load combinations. Pile-soil interaction was
modelled using 3 nonlinear springs for each soil layer (Two horizontal and one vertical
spring). The nonlinear properties for all horizontal springs are governed by p-y curve (i.e.
Lateral Load Vs. deflection of the pile), vertical springs for all layers except bottom most
layer by t-z curves (i.e. Skin Frictional resistance vs. deflection along pile) and vertical spring
for bottom most layer by Q-z curve (i.e. Tip resistance Vs. Pile Tip Deflection). These curves
are generated using API RP 2A-WSD. For Earthquake analysis these curves were linearized
(i.e. soil was assumed to behave linearly). The estimated skin friction and end bearing are
shown in Table 5.
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
0 1 2 3 4
Acc
lera
tio
n (
m/s
2 )
Period (s)
Accleration Spectrum
33
DEPTH (m) SKIN FRICTION
(Pa) Tip Resistance
(Pa)
1.5 1957.5 -
3 5872.5 -
4.5 9787.5 -
6 13702.5 -
7.5 17617.5 -
9 21532.5 -
10.5 25447.5 -
12 29362.5 -
13.5 33277.5 -
15 37192.5 1620000
Table 3 Soil Parameters for Different Layers
5.2.4. Cyclones
The appropriate loads as explained in earlier were considered and the obtained deflection
profiles were shown in Fig.15. The deflections at the platform level are within the allowable
limit of l/150. The capacity of the members is checked using API RP 2A WSD. The
utilization of monopole is 0.41 and monopile is 0.42. The details calculations are explained
below.
Max Deflection - 0.015 m
Max Rotation - 0.042o
Max Deflection - 0.106 m
Max Rotation - 0.29o
Normal Sea State Severe Sea State
Fig. 15 Deflected Profiles for Various Sea States
34
5.2.4.1. Axial Compression:
Allowable Axial Compression Fa is determined from the AISC formulas for cylindrical
members based on the diameter to thickness ratio. When the ratio is less than 60 then local
buckling stress are not checked and if the ratio is greater than 60 Fy is substituted with critical
local bucking stresses (Fxe or Fxc whichever is less).
Fa =
[1 −(Kl/r)2
2Cc2 ] Fy
53 +
3(Kl/r)8Cc
+1(Kl/r)3
8Cc3
for (Kl/r) < Cc
Fa =12π2E
23(Kl/r)2 for (Kl/r) ≥ Cc
Where,
Cc=(12π2E
Fy)
1
2
E = young′smodulus of elasticity, Mpa
K = effective length factor
l = unbraced length, m
r = radius of gyration, m
The members having D/t ratio more than 60 local buckling due to axial compression should
be investigated.
5.2.4.2. Elastic Local Buckling Stress
Elastic buckling stress can be determined from:
Fxe = 2CEt/D
Where,
C = critical elastic buckiling coefficient,
D = outside diameter , m,
t = wall thickness, m.
5.2.4.3. Inelastic local buckling Stress.
Inelastic local buckling stress can be determined from:
Fxc = Fy [1.64 − 0.23 (D
t)
1/4
] 2CEt/D.
35
In our case allowable Fa for Beam element is determined as follows:
Diameter, D(m) = 1.2
Wall Thickness, t (m) = 0.025
Young's modulus, E(Mpa) = 2.10E+05
Yield Strength, Fy(Mpa) = 250
Unbraced Length, l (m) = 27.5
Effective length factor K = 2
Radius of gyration, r(m) = 0.346554469
Moment (KNm) = 850
Vertical load (KN) = 250
Area of the section A(m2) = 0.061575216
Moment of inertia I(m) = 0.007395183
Sectional Modulus Z(m3) = 0.012325306
Radius of Gyration R(m) = 0.346554469
Slenderness ratio λ = 158.7052106
D/t ratio = 50
Cc = 315.4133991
Kl/r ratio = 158.7052106
As D/t ratio is greater than 60 we have to check for local buckling and substitute critical local
buckling stress stresses (Fxe or Fxc whichever is less) for Fy. In the calculation of local
buckling stress the value of critical elastic coefficient “C” has been taken as 0.3 as per API.
The allowable compression and calculated axial stress are as below.
Local Elastic Buckling Fxe (Mpa) = 2520
36
Local Inelastic Buckling Fxc (Mpa) = 257.7872
Allowable Axial
Compression Fa(Mpa) = 118.5
Calculated Axial Stress fa cal(Mpa) = 4.06
5.2.4.4. Allowable Bending Stress:
The allowable bending stress can be determined as following:
Fb = 0.75 Fy for D
t≤
10340
Fy
Fb = [0.84 − 1.74 FyD
Et] Fy for
10340
Fy<
D
t≤
20680
Fy
Fb = [0.72 − 0.58 FyD
Et] Fy for
20680
Fy<
D
t≤ 300
Here in our case the D/t ratio satisfies the second condition and as per API the stresses are as
follow
Allowable Bending Stress Fb(Mpa) = 184.107
Calculated Bending Stress Fb cal(Mpa) = 68.96
Interaction Ratio
fa cal/Fa + fb cal/Fb = 0.408
Similarly in case of Static analysis for Pile element the interaction ratio is 0.41.
5.2.5. Earth Quake
The occurrence earthquake during normal sea state is considered in this case. The deflections
at the top of substructure are 0.142 m and less than allowable limit of l/150. From the
deflections it can be observed that the design of structure is mainly governed by earthquake.
The capacity of the members is checked using API RP 2A WSD. The utilization of monopole
is 0.35 and monopile is 0.37. The detailed calculations are given below
37
5.2.5.1. Member Capacity for Earthquake Load Combination:
For Beam Element
Allowable Axial
Compression Fa(Mpa) = 118.5
Calculated Axial Stress fa cal(Mpa) = 4.060075079
Allowable Bending Stress Fb(Mpa) = 184.107
Calculated Bending Stress Fb cal(Mpa) = 57.92
Interaction Ratio fa cal/Fa + fb cal/Fb = 0.348
For Pile Element
Allowable Axial
Compression Fa(Mpa) = 143.885
Calculated Axial Stress fa cal(Mpa) = 3.962
Allowable Bending Stress Fb(Mpa) = 184.107
Calculated Bending Stress Fb cal(Mpa) = 63.8524
Interaction Ratio fa cal/Fa + fb cal/Fb = 0.37436
5.2.6. Boat Impact
Boat landing is considered for small boats with a weight less than 25 tons which will be used
to transporting people for inspection and maintenance of equipment. Controlled boat velocity
of 0.5 m/s is considered for analysis. The kinetic energy due to boat impact is equated to the
work done by the structure to find an equivalent point load at water level. This load is applied
on the structure along with operational sea state condition. The deflection during boat impact
is 0.12 m and less than allowable limit of l/150. The capacity of the members is checked
using API RP 2A WSD. The utilization of monopole is 0.42 and monopile is 0.44.
5.2.6.1. Member Capacity for Boat Impact Combination:
For Beam Element
38
5.2.7. Platform
The platform is provided for supporting all the equipment’s required to measure. Platform
consists of central rigid circular beam and main beams radiating from the central beam. Main
beams are connected with secondary beams. Trapezoidal plates are resting over the main
beams, over which all equipment loads such as wind turbine, LiDar , solar panels, wind
measurement instruments and batteries are resting. The platform is analyzed for the ultimate
and service conditions as per of IS 800:2007. The detail design of structural members is given
below.
5.2.7.1. Material Properties
Central rigid beams
= ISMC 150
Length of rigid beam
= 620 mm
Main beams
= ISMC 150
Length of main beams
= 1300 mm
Allowable Axial Compression Fa(Mpa) = 143.885
Calculated Axial Stress fa cal(Mpa) = 4.06
Allowable Bending Stress Fb(Mpa) = 184.107
Calculated Bending Stress Fb cal(Mpa) = 71.39
Interaction Ratio fa cal/Fa + fb cal/Fb = 0.41602
For Pile Element
Allowable Axial Compression Fa(Mpa) = 143.885
Calculated Axial Stress fa cal(Mpa) = 4.628
Allowable Bending Stress Fb(Mpa) = 184.107
Calculated Bending Stress Fb cal(Mpa) = 74.64
Interaction Ratio fa cal/Fa + fb cal/Fb = 0.4376
39
Secondary beams
= ISMC 75
Length of secondary beams = 1290 mm
Plate thickness
= 16 mm
(Increased 4mm for marine consideration)
Steel for plates /Beams
= E250 (As per IS 2062:2011)
Field welds
= E410
Unit weight of steel
= 78.5kN/m3
5.2.7.2. Loads & Load combinations
Loadcase 1
Self weight of the
beam
Loadcase 2
Self weight of the
plates
Loadcase 3
LiDar weight = 0.765 kN
radius of central rigid = 0.6 m
circumference of
central rigid portion
= 3.768 m
U.d.l. of LiDar = 0.20 kN/m
Loadcase 4
Windturbine
2nos
= 0.981 kN
one turbine weight = 0.4905 kN
Loadcase 5
Solar panels +
mounting accessories = 0.491+ 0.343
= 0.834 kN
u.d.l for solar panels = 0.2836735 kN/m
Loadcase 6
Batteries & enclosures = 2.4525+0.981
= 3.433 kN
radius of central rigid = 0.6 m
circumference of
central rigid portion
= 3.768 m
40
U.d.l. of battery = 0.91 kN/m
Loadcase 7
Wind measurement
instruments = 0.491 kN
Loadcase 8
Central plate
area of central plate = 1.1304 m2
volume of central plate = 0.0180864 m3
weight of central plate = 1.4197824 KN
u.d.l of central plate = 0.3768 kN/m
Loadcase 9
People movement = 5kN/m2 (From IS875)
Loadcase 10
For ultimate condition = 1.5(L.C1+L.C2+L.C3+L.C4+L.C5+L.C6+L.C7+L.C8+L.C9)
Loadcase 11
For servicability
condition = 1.0(L.C1+L.C2+L.C3+L.C4+L.C5+L.C6+L.C7+L.C8+L.C9)
5.2.7.3. Staad Results
S.No Members B.M(kNm) S.F(kN) Deflections(mm)
1
Main
beams 10 10.5 3.86
2 Rigids 21 12.166 0.279
3 Sec beams 0.691 1.687 0.736
Main beams & Central Rigid beam
ISMC150 (2Sections faced front to front)
From SP -6
A = 4176 mm2
H = 150 mm
B = 150 mm
D = 132 mm
tf = 9 mm
41
tw = 5.4 mm
Ixx = 15588000 mm4
Iyy = 2046000 mm4
Zxx = 204800 mm3
Zyy = 38800 mm3
Zp = 272384 mm4
r1 = 10 mm
5.2.7.4. Sectional Classification
ε =
= 1
From Table 2 IS 800:2007
d/tw = 132/5.4 = 24.4444 < 84ε
84
Hence the section is
plastic
5.2.7.5. Shear Capacity
According to Cl 8.2.1.2 IS 800:2007
V < 0.6Vd
Vd = Vn
γmo
Vn = Av x fyw
Av = Ah
(b+h)
= 2088 mm2
42
Vn = 301385.7
Vd = 273.987 kN
0.6Vd = 164.3922 kN
V < 0.6Vd
Hence the section is safe in shear condition
5.2.7.6. Moment Capacity
M < Md
Md = βb Zpfy
γmo
Since the section is plastic
βb = 1
Md = 62.26977 kNm
M < Md
Hence the section is safe
5.2.7.7. Check for deflections
Allowable deflection
From table 6 IS 800-2007
For Main beams = L/180 = 7.22222 mm
For rigid beams = L/300 = 2.06667 mm
Deflection of main beam = 3.86 mm safe in deflection
Deflection of rigid beam = 0.279 mm safe in deflection
5.2.7.8. Check for web buckling
Assume bearing length = 0 mm
Ab = (b+n1) tw
43
n1 = 75
Ab = 405 mm2
Slenderness ratio,λ = 2.5d/t
= 61.11111
From Table 9c of IS 800-2007
fcr = 167 N/mm2
Capacity of the section
= 67.635 kN
Hence the section is safe against web buckling
5.2.7.9. Check for web bearing
Fw = (b+n2) twfy
γmo
n2 = 2.5(R+tf)
= 47.5 mm
Fw = 58.29545 kN
Hence the section is safe against web bearing
5.2.7.10. Check for stiffeners
According to Cl 8.6.1.1 IS 800-2007
d/tw <200ε Not required for stiffeners
d/tw = 24.44444 < 200
Hence transverse and longitudinal stiffeners not required.
5.2.7.11. Check for compression flange buckling
According to Cl 8.6.1.7 IS 800-2007
d/tw < 345 ε 2
24.444444 < 345
44
Hence no buckling of compression flange into web occurs.
5.2.7.12. Secondary beams
ISMC75
(2Sections faced front to front)
From SP -6
A = 867 mm2
h = 75 mm
b = 40 mm
d = 67.7 mm
tf = 7.3 mm
tw = 4.4 mm
Ixx = 760000 mm4
Iyy = 126000 mm4
Zxx = 20300 mm3
Zyy = 4700 mm3
Zp = 24766 mm4
r1 = 8.5 mm
5.2.7.13. Sectional Classification
ε =
= 1
From Table 2 IS 800:2007
d/tw = 17.04545 < 84ε
Hence the section is
plastic
5.2.7.14. Shear Capacity
According to Cl 8.2.1.2 IS 800:2007
V < 0.6Vd
45
Vd = Vn
γmo
Vn = Av x fyw
Av = Ah
(b+h)
= 565.4348 mm2
Vn = 81615.88
Vd = 74.19625 kN
0.6Vd = 44.51775 kN
V < 0.6Vd
Hence the section is safe in shear condition
5.2.7.15. Moment Capacity
M < Md
Md = βb Zpfy
γmo
Since the section is plastic
βb = 1
Md = 5.628636 kNm
M < Md
Hence the section is safe
5.2.7.16. Check for deflections
Allowable deflection
From table 6 IS 800-2007
For secondary beams = L/300 = 4.3 mm
46
Deflection of secndary beam = 0.736 mm safe in deflection
5.2.8.17. Check for web buckling
Assume bearing length = 0 mm
Ab = (b+n1) tw
n1 = 37.5
Ab = 165 mm2
Slenderness ratio,λ = 2.5d/t
= 38.46591
From Table 9c of IS 800-2007
fcr = 197 N/mm2
Capacity of the section
= 32.505 kN
Hence the section is safe against web buckling
5.2.7.18. Check for web bearing
Fw = (b+n2) twfy
γmo
n2 = 2.5(R+tf)
= 39.5 mm
Fw = 39.5 kN
Hence the section is safe against web bearing
5.2.7.19. Check for stiffeners
According to Cl 8.6.1.1 IS 800-2007
d/tw <200ε Not required for stiffeners
d/tw = 17.04545 < 200
Hence transverse and longittudinal stiffeners not required.
47
5.2.7.20. Check for compression flange buckling
According to Cl 8.6.1.7 IS 800-2007
d/tw < 345 ε 2
17.045455 < 345
Hence no buckling of compression flange into web occurs.
5.2.7.21. Welded Connection design
Connection between the rigid beams and main beams
S.F = 10.5 kN
B.M = 10 kNm
Factor of safety = 1.5 (from table 6 of IS 800-2007)
Web connection
Maximum size of weld = 3.9 mm (table 21 of IS 800-2007)
Minimum size of weld = 3 mm
Assume weld size of = 3.5 mm
Throat thickness,t = 2.45 mm
Strength per 1mm length of weld
= 386.6436 N/mm
Length of the weld = 27.15679 mm
Hence provide weld of 3.5 mm for a length of 30
mm along the
web
Flange connection
V = 66.7 kN
Maximum size of weld = 7.5 mm (table 21 of IS 800-2007)
Minimum size of weld = 3 mm
Assume weld size of = 6 mm
Throat thickness,t = 4.2 mm
Strength per 1mm length of weld
= 662.8176 N/mm
Length of the weld = 100.5807 mm
Hence provide weld of 6 mm for a length of 104
mm along the
flange
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Connection between the secondary beams and main beams
S.F = 1.687 kN
Factor of safety = 1.5 (from table 6 of IS 800-2007)
Web connection
Maximum size of weld = 4.4 mm (table 21 of IS 800-2007)
Minimum size of weld = 3 mm
Assume weld size of = 3 mm
Throat thickness,t = 2.1 mm
Strength per 1mm length of weld
= 331.4088 N/mm
Length of the weld = 5.09039 mm
Hence provide weld of 3 mm for a length of 8
mm along the
web
6. Installation procedure
The steel Monopiles will be fabricated and transported to the site from shore with the help of
barges. Approximate weight of the pile is around 50tonnes. These piles are constructed from
welded steel tubular sections which are driven vertically into the sea bed. The piles support
the weight of the platform and the instruments primarily using the friction between the pile
walls and the sea bed. The monopile will be fabricated at a suitable fabrication yard and
transported to site. A brief typical installation sequence is as follows:
Transportation of monopile to offshore site via vessel, barge or float-out
Up-ending the pile by Jack-up crane vessel with buoyancy assistance if required
Monopile is lowered to seabed location, while pile weight provides initial sea bed
penetration.
Hammering the pile till the desired depth. (Soil plugging if any will removed till
desired depth is achieved).
Installation of platform at the top which is followed by the installation of LiDar
equipments.
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Transporting to location Lifting with crane
Launching Positioning
Driving by hammer Completion of Driving Monopile
Removing of Hammer after driving
Fig. 16 Installation methodology for wind mast
6.1. Decommissioning procedure
For the wind mast it is envisaged that the foundation pile would be cut to below the natural
level of the seabed to such a depth to ensure that the remains are unlikely to become
uncovered. Complete removal of the pile below the seabed is considered neither practical nor
environmentally desirable. The appropriate depth of removal will depend on the sea-bed
conditions and site characteristics at the time of decommissioning which is in line with IMO
standards as complete removal of the foundations would involve an unacceptable risk to the
marine environment and are likely to involve extreme cost. If an obstruction exists above
seabed following the decommissioning which is attributable to the Met Mast, it will be
marked so as not to present hazard to other sea users.
Decommissioning of pile structure:
50
Divers are deployed to inspect pile footing and reinstate lifting attachments if
necessary
Jack-up barge or heavy lift vessel is mobilized to the site
Any scour protection that has been placed around the support structures should be
removed
Crane hooks are deployed from decommissioning vessel and attached to the lift points
The pile is cut below the natural seabed, following the pile removal the seabed is
inspected for debris and any found is subsequently removed.
6.2. Construction and operational impact assessment
6.2.1. Noise level
The noise and the disturbances created during construction phase is very minimal. Noise level
generated by pile driving for such a small diameter is <50dB. Hence the noise generated
during the construction phase will not affect the aquatic environment nearby. Transport of
construction material to the site will restricted in daytime.Use of personal protective devices such
as ear-muff, ear-pugs etc. will be enforced wherever necessary.Periodic maintenance of
Construction machinery and transportation vessels will be undertaken to reduce the noise impact.
Since the construction phase is for very short term it will have negligible effect.
6.2.2. Air Environment
There will not be any dust emission during a pile driving in sea water. There will be no on-
site burning of any waste arising from any construction activities. However Nose masks will
be provided to construction workers, while carrying out operations.
6.2.3. Water Environment
As the construction phase is for short period and also the number of workers involved is of
less quantity impact on water quality is negligible. Sanitation facilities will be made available
for disposal of sewage generated by the workers as per SPCB norms. Since, the construction
activity happens with the help of vessels proper sanitation facilities will be provided in order
to maintain hygienic condition of labourers.
6.2.4. Fishery
There are not much commercial fish trawling operations off Jakhau port. However drifts and
other local nets are commonly used by local fishermen community. These operations are not
hampered much during construction as well as operational activities.
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7. Project Schedule and cost estimates
7.1 Project Schedule
The period of completion for the project is about 60days. Preparation of drawing, design will
constitute about 20 days .Fabrication of the structure and mobilization to the site is will take
about 40days. Installation will take about another 30days.
7.2 Cost estimate
The total cost of the project including Wind Profiler, mobilization, demobilization and
installation is Rs 493 lakhs.