mnsea may 2018 presentation barr v0...strain readings moment and power vs. time power moment....
TRANSCRIPT
5/2/2018
1
wind turbine foundationsstructural design principles & practices
MNSEA tradeshow & seminarMay 8, 2018
Christopher Kopchynski, PE,Barr Engineering Co.
Introduction to Barr
Engineering
Barr’s presenter – Mr. Christopher A. Kopchynski
• [email protected]• 30 years of structural engineering
experience• 20 years of wind turbine foundation
experience• licensed professional engineer in 7
Canadian provinces and 12 U.S. states
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Barr Engineering
Co.
• www.barr.com• corporate headquarters:
Minneapolis, Minnesota• employee owned, 700 people• engineering wind turbine
foundations since 1994• 370 facilities• 21,700 wind turbines• 38,500 MW of nameplate capacity• 4,000 MW in construction• 2,000 MW in design
integrated process
Mechanical &ElectricalFactors
The PhysicalWorld
StructuralFactors
Materials
GeotechnicalFactors
Foundation
Construction
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overturning moment is (vi)king
Aerodynamic Forces
Overturning Moment
Vertical Load
Horizontal Load
• large lever arm
• high aerodynamic thrust
• vertical load and horizontal load relatively small50
m to
120
m
300kN to 1100 kN
15MN-m to 150 MN-m
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dynamic structural behavior
TowerStrain_shortened_Barr.wmv
strain readings
moment and power vs. time
POWER
MOMENT
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Foundation Rotation vs. Momentrotation verses moment
fatigue loads
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24220
21553
24606
21285
22850
21537
22786
20914
22424
23771
21261
24044
22330
23063
21178
24724
20924
24391
21669
20000
20500
21000
21500
22000
22500
23000
23500
24000
24500
25000
10 15 20 25 30 35 40
Momen
t (kN
‐m)
Elapsed Time (seconds)
Moment verses Time
design fatigue spectrum
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represented by sets of corresponding:
• ranges, Sr,I
• means, Sm,I
• cycles, i=1 to n
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wind turbine foundation design steps
FAIL
PASS
FAIL
PASS
FAIL
FAIL
PASS
1
23
PASSPASS
design input - tower bottom flange dimensions
• provided by original equipment manufacturer (OEM)
• flange outside and inside diameter• bolt circle inside and outside diameter• number of bolts• bolt hole diameter• flange thickness• tower shell outside diameter• tower shell thickness
design input – foundation loads
• provided by OEM• normal extreme• abnormal extreme• operating 1% exceedance• operating 0.1% exceedance• markov matrix fatigue loads• seismic - tower & turbinecomponent weights
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design input – stiffness requirements
• provided by OEM• foundation rotational and lateral stiffness
design input – geotechnical soil properties
• provided by project• soil chemistry• groundwater level• ground improvement
wind turbine foundation design steps
FAIL
PASS
FAIL
PASS
FAIL
FAIL
PASS
1
23
PASSPASS
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design codes• International Building Code• American Concrete Institute ACI-318• American Institute of Steel Construction
AISC 360• American Society of Civil Engineers
ASCE 7• state and local building codes
industry standards
• International Electro Technical Commission IEC 61400-1
• Germanisher Lloyd GL Wind Guidelines 1.1
• Det Norske Offshore Standard DNV-OS-C502
• American Wind Energy Association, ASCE/AWEA RFP2011
technical references
• DNV, Guideline for Design of Wind Turbines
• Arya, O’Neill and Pincas, Design of Structures and Foundations for Vibrating Machines
• Fahey, Soil Stiffness
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new standards
• DNV GL ST-0126, “Support Structures for Wind Turbines”
• IEC 61400-6, “Wind Turbines – Part 6: Tower and Foundation Design Requirements”.
wind turbine foundation design steps
FAIL
PASS
FAIL
PASS
FAIL
FAIL
PASS
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PASSPASS
materials - concrete
• minimum 4500 psi (31 MPa), typical 5000 psi (35 MPa)
• rare: extremely large loads 6000 psi (41 MPa)
• ¾” (19m) to 1 ½”(38mm) coarse aggregate size• fly ash common• non-alkali silicareactive aggregates
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materials – reinforcing steel
• ASTM A615 grade 60 ksi (414 MPa) or grade 75 (517 MPa)
• plain deformed bars• #4 (12mm) to#11 size (36mm)• rarely:large loads #14 size (43mm)
materials – anchor bolts
• cold formed threads• ASTM A615, grade 75 (517MPa)• ASTM A722, type 1 (827 Mpa)• custom grade 90 (620 Mpa)• common size 1 3/8” (35mm)• rare: large loads 1 ¾” (46mm)• pvc sleeves
materials – template ring and embedment plate
• ASTM A36 (248 MPa)• 1 in (25mm) to 2 in (50mm) thick• dimensions matching tower flange
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materials – bottom flange grout
• modified cementitious or epoxy• 8000 psi (55MPa) to 15000 psi
(103 MPa)• 1 ½ in (38mm) to 3 in (75mm)
thick• formed with shoulders or placed
in grout pockets• rare: for large loads deep grout
pockets
wind turbine foundation design steps
FAIL
PASS
FAIL
PASS
FAIL
FAIL
PASS
1
23
PASSPASS
check a1 –global
overturning stability
• use unfactored extreme loads• use characteristic dead load resistance• per AWEA/ASCE FS>1.5• per IBC 0.6W>1.0
− W=stabilizing weight of the foundation
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check a2 –foundation
contact extreme load
• GL wind guidelines• greater than 50% contact• use unfactored extreme loads• use characteristic dead load resistance
check a3 –foundation contact 1%
exceedance load
• GL wind guidelines• 99.5% to 100% contact• use unfactored normal loads• use characteristic dead load resistance
check a4 –bearing
capacity
• allowable stress design (ASD) check• allowable bearing capacity per
geotechnical report• assume DNV RISO soil stress
distribution• applied normal operating, normal
extreme, abnormal extreme, and seismic less than allowable
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riso soil distribution
stiffness
• use formulas from Arya• assume rigid foundation on elastic medium• reduce small strain modulus considering soil strain using
Fahey
shear modulus ratio:
• stiffness must be greater than minimum specified
rotational stiffness:
wind turbine foundation design steps
FAIL
PASS
FAIL
PASS
FAIL
FAIL
PASS
1
23
PASSPASS
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check b1 –anchor bolt
• use AISC 360• ultimate limit state (ULS) design check• factored loads and material resistance
factors• select pre-tension based on maximum
fatigue load and increase 20 to 30% to account for losses
check b2-grout
• select grout thickness and strength• use ACI 318• ULS check
check b3 –embedment
plate
• select embedment plate thickness• use AISC 360• ULS check• nut to nut bending• nut to edge bending• rupture of washer through plate
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check b4 –foundation connection
• use ACI 318• select embedment ring
height above foundation
• ULS checks• tower flange pedestal
bearing• vertical reinforcing
moment strength
wind turbine foundation design steps
FAIL
PASS
FAIL
PASS
FAIL
FAIL
PASS
1
23
PASSPASS
check d –footing
bottom and top
reinforcement
• use ACI 318• ULS check• one-way footing bending• top reinforcement upwind bending• bottom reinforcement downwind
bending• two way moment/shear transfer
between the pedestal and footing
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wind turbine foundation design steps
FAIL
PASS
FAIL
PASS
FAIL
FAIL
PASS
1
23
PASSPASS
check c –footing
concrete shear
strength
• use ACI 318• ULS design check• one-way shear• select coarse aggregate size• above code: use Concrete International
technical reference to account for size effects
wind turbine foundation design steps
FAIL
PASS
FAIL
PASS
FAIL
FAIL
PASS
1
23
PASSPASS
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check e –fatigue limit
state (FLS)
• use DNV OS C502• footing concrete compression in
bending• footing concrete one-way shear• pedestal concrete bearing• footing top and bottom reinforcing in
tension• pedestal/footing vertical reinforcing
typical constructiom
sequence
site preparation
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excavation
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mud mat
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lay down bearing bars
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place remaining
bottom bars
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set anchor bolt cage
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place top mat rebar
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set forms
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place footing
concrete
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finish top of footing
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set conduit and
grounding
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set pedestal form & place
concrete
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remove pedestal
forms
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backfill and compact soil
over foundation
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finish grade site
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extend conduit into transformer
pad
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set bottom tower and
grout
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tension anchor bolts
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erect remaining
turbine parts
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commission wind farm
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questions?