3 - Structural Integrity Evaluation of Offshore Wind Turbines - Giuliani

Structural Integrity Evaluation of Offshore Wind Turbines

Luisa Giuliani Franco Bontempi

[email protected] [email protected]

Structural and Geotechnical Engineering Department

University of Rome “La Sapienza”

Presentation outlineEARTH&SPACE 2010

STRUCTURAL INTEGRITY OF OFFSHORE WIND TURBINES

What is it and why to care about it

STRATEGIES AND MEASURE OF ACHIEVEMENT

Robustness and vulnerability

A CASE STUDY

Investigation of an offshore turbine response to a ship collision

CONCLUSIONS

Conclusive evaluations on application and methodology

L. Giuliani, F. Bontempi - Structural Integrity Evaluation of Offshore Wind Turbines 2/26

A CASE STUDY


STRATEGIES AND MEASURE OF ACHIEVEMENT


CONCLUSIONS


STRUCTURAL INTEGRITY OF OFFSHORE WIND TURBINES


Why care about structural integrity?EARTH&SPACE 2010

MIDDELGRUNDENS VINDMØLLELAUGOffshore wind farm in Øresund, outside Copenhagen harbor, 2000)

Operator: Dong EnergyOwner: 50% investor cooperative

50% municipalityOfficial website: http://www.middelgrunden.dk


L. Giuliani, F. Bontempi - Structural Integrity Evaluation of Offshore Wind Turbines

Why care about structural integrity?

4/26

EARTH&SPACE 2010

RUNAWAY EVENT(Jutland, 2008)

1. High wind and breaking system failure 2. Blades spin out of control and fail

3. Blade debris collided with the tower4. Turbine tower collapses to the ground.

Why care about structural integrity?EARTH&SPACE 2010

RUNAWAY EVENT(Jutland, 2008)

1. High wind and breaking system failure 2. Blades spin out of control and fail

3. Blade debris collided with the tower4. Turbine tower collapses to the ground.

DISPROPORTION BETWEEN

CAUSE AND EFFECT


Disproportionate collapse in standardsEARTH&SPACE 2010

ASCE 7ASCE 7--02, 200202, 2002

The structural system shall be able to

sustain local damage or failure with the

overall structure remaining stable and not

be damaged to an extend disproportionate

to the original local damage

GSA guidelines, 2003GSA guidelines, 2003

the building must withstand as a minimum,

the loss of one primary vertical load-bearing

member without causing progressive

collapse

Unified facilities criteriaUnified facilities criteria

UFC 4UFC 4--023023--03, DoD 200503, DoD 2005

All new and existing buildings with three

stories or more in height must be designed

to avoid progressive collapse

Model code 1990Model code 1990

Structures should withstand accidental

circumstance without damage disproportionate

to the original events (insensitivity requirement)

ISO/FDIS 2394, 1998ISO/FDIS 2394, 1998

Structures and structural elements should

satisfy, with proper levels of reliability:

-exercise ultimate state requirements

- load ultimate state requirements

- structural integrity state requirements

EN 1991EN 1991--11--7:2006 7:2006

Structures should be able to withstand

accidental actions (fires, explosions, impacts) or

consequences of human errors, without

suffering damages disproportionate to the

triggering causes

CODESAMERICAN EUROPEAN


Structural integrityEARTH&SPACE 2010

STIFFNESSService limit

states (SLS)

RESISTANCE

ST

RU

CT

UR

AL

SA

FE

TY

Ultimate limit

states (ULS)

SECTIONSSECTIONS

OR ELEMENTSOR ELEMENTS

?

R > S

f < ff < fadmadm

RESISTANCE

TO

EXCEPTIONAL

ACTION

Structural

integrity limit

state (SILS)

STRUCTURAL

SYSTEM

verification on

FAILURE IS PREVENTED

FAILURE IS PRESUMED


OFFSHORE STANDARD, DNVOFFSHORE STANDARD, DNV--OSOS--J101, 2004J101, 2004

The structural system shall be able to resists accidental loads and

maintain integrity and performance of the structure due to local damage

or flooding.

CONSIDERED LIMIT STATESCONSIDERED LIMIT STATES

ACCIDENTAL ACTIONSACCIDENTAL ACTIONS

Structural integrity for OWTEARTH&SPACE 2010


ULSUltimate Limit

States

ALSAccidental Limit

States

FLSFatigue Limit

States

SLSServiceability

Limit States

maximum load

carrying resistance

failure due to the

effect of cyclic

loading

damage to

components due to

an accidental event

tolerance criteria

applicable to normal

use


STRUCTURAL INTEGRITY OF WIND TURBINE


STRATEGIES AND MEASURE OF ACHIEVMENT


A CASE STUDY


CONCLUSIONS







Different factors affecting structural integrityEARTH&SPACE 2010

P(F) = P(D|H) P(F|DH)P(H) x x

occurrence

of collapse

VULNERABILITY ROBUSTNESSEXPOSURE VULNERABILITY ROBUSTNESSEXPOSURE

[Fa

be

r, 2

00

6]

[Ellin

gw

oo

d,

19

83

]

STRUCTURALNON STRUCTURAL

MEASURES

avoid dispropor. collapselimit initial damageevent control

2) reduce

the effects of the

action

3) reduce

the effects of a

failure

1) reduce

the action

damage is caused in

the structure

critical event occurs

near the structure

damage spreads in

the structure


EVENT CONTROL

Non structural measuresEARTH&SPACE 2010

Malfunctioning and fire

Natural actions

Ship collision

Malevolent attack

System control

Protective barriers

Sacrificial structures

Surveillance


a. Difficult to prevent every possible accidental event

b. Difficult to protect WT (exposed to natural action)

c. Difficult to surveille WT (wide and isolated area)

reduce the occurrence

of the action

reduce the exposure

of the structure

1)1) REDUCE THE ACTIONREDUCE THE ACTION

Structural measuresEARTH&SPACE 2010


TOP

DOWN

Identification of failures at meso-level

(intermediate components)

Identification of failures at micro level

(basic components)

BOTTOM

UP

Deductive (top-down):

critical event is modeled

Inductive (bottom-up):

critical event is irrelevant

ROBUSTNESS

2) REDUCE THE EFFECTS2) REDUCE THE EFFECTS

OF THE ACTIONOF THE ACTION

3) REDUCE THE EFFECTS3) REDUCE THE EFFECTS

OF A FAILUREOF A FAILURE

VULNERABILITY

SHIP COLLISION DAMAGED COMPONENTS

d

)d(RI

∆

∆=

Structural robustnessEARTH&SPACE 2010


structure B

d

P

s

STRUCTURE B:

P

s

ROBUSTNESS CURVES

P (performance)

structure A

STRUCTURE A

damaged

integer

∆P

damaged

more performant, less resistant

integer

(damage level)

∆P∆P

more performant, less robust less performant, more robust

PERFORMANCE ultimate resistance

DAMAGE LEVEL# removed elements

STRUCTURAL ROBUSTNESS: Insensitivity to local failure

(ASCE/SEI-PCSGC, 2007 – Betonkalender, 2008)

Proposed robustness measure:

decrement of resistance that corresponds

to an increment of damage in the structure

EARTH&SPACE 2010


28

0 1 2 --- 8 d

λExact maxima and minima curves

EXHAUSTIVE INVESTIGATIONEXHAUSTIVE INVESTIGATION

1

Cd EX.

81

Exhaustive combinations

Cd =E!

d! × (E-d)!

Ctot = Σd Cd = 2E

0

for D = E

D

a structure of 8 elements is considered as example

Robustness curves

EARTH&SPACE 2010


0 1 2 --- 8 d

Approximated maxima and minima curves

HEURISTIC OPTIMIZATIONHEURISTIC OPTIMIZATION

ERROR! (non cons.)

14 2

Reduced combinations

= 1

d>1

Cd =

= 2 ×[E-(d-1)]

= Ed=1

d=0

0

D

Ctot = Σd Cd = E2 + 1

for D = E

1

28

Exhaustive combinations

Cd =E!

d! × (E-d)!

Ctot = Σd Cd = 2E

0

for D = E

Dexponentialexponential

polynomialpolynomial

8

Cd EX.

Cd RED.

a structure of 8 elements is considered as example

Robustness curves

8/3111/31

Stiff

beam

s (

fle

x.

behavio

ur)

Stiff

colu

mns (

shear-

type)

ST

RU

CT

UR

AL

BE

HA

VIO

UR

16 17 18

13 14 15

9 10 1211

5 6 87

1 2 43

19 20 21

λλλλλλλλgg

16 17 18

13 14 15

9 10 1211

5 6 87

1 2 43

19 20 21

λλλλλλλλgg

SHEAR-TYPE FRAME ROBUSTNESS

00

,51

17 1 2 3 4 5 6 7 8 9 10

Damage Level

PU

[a

d]

MAX MIN

FLEX-TYPE FRAME ROBUSTNESS

00

,25

0,5

0,7

51

0 1 2 3 4 5 6 7 8 9 10Damage Level

PU

[a

d]

MAX MIN

λg

5 6 87

9 10 12

13 14 15

16 17 18

19 20 21

41 2 3

11

λg

14

17

1513

18

19

5 6 87

1211

41 2 3

9 10

16

20 21

1 2 43

5 6 87

9 10 1211

13 14 15

16 17 18

19 20 21

λg

λg

14

17

20

1513

1816

2119

5 6 87

41 2 3

9 10 1211

EARTH&SPACE 2010


Comparison between different design solutions

EARTH&SPACE 2010


Robustness applied to OWT

OWT ROBUSTNESS COMPARISON

between two jacket structures between two support types






A CASE STUDY


CONCLUSIONS





A CASE STUDY




EARTH&SPACE 2010


OWT ship collision investigation

EARTH&SPACE 2010



OWTSTRUCTURE MODELING

Pointed mass for

modeling rotor and

nacelle.

One-dimensional elements

for leg and tower with

elastic-plastic behavior

(spread plasticity).

Soil interaction

accounted with 3D

finite elements,

which behave

elastically. Zone

extension calibrated

in order to minimize

boundary effects.

Typical OWT:

5-6 MW power

36 m water depth.

S355 steel monopile with

hollow circular section;

diameter and thickness

vary along the tower.

4 diagonal legs

connected to 4

45 m long

foundation piles,

40 m deepened

into the ground.

EARTH&SPACE 2010



OWTLOAD SCENARIOS SHIP IMPACT MODELING

Only self-weight is assumed to act on

the turbine at the moment of impact.

Three different scenarios are

considered for ship collision point:

A. Impact on one

diagonal leg under

the seabed (model

node #17);

700 ton700 ton

AA

700 ton700 ton

AA

EARTH&SPACE 2010








A. Impact on one

diagonal leg under

the seabed (model

node #17);

B. Impact at the

seabed (model

node #38);

700 ton700 ton

BB

700 ton700 ton

BB

EARTH&SPACE 2010








A. Impact on one

diagonal leg under

the seabed (model

node #17);

B. Impact at the

seabed (model

node #38);

C. Impact on the

tower above the

seabed (model

node #548).

t [s]

F [MN]

0.5 1.5 2.00.0

7

Ship impact is modeled by means

of an impulsive force acting on

the collision point.

The value of the force is 7 MN (ca.

700 ton) and the total length of

the impulsive function is 2 s.

Nonlinear dynamics analyses are

carried on the structure.

700 ton700 ton

CC

EARTH&SPACE 2010


Nonlinear dynamic investigations

SCENARIO A

time: 0.025 s

time: 0.0 s

EARTH&SPACE 2010



SCENARIO A

time: 0.3 s

EARTH&SPACE 2010



SCENARIO A

time: 0.3 stime: 0.5 s

EARTH&SPACE 2010



SCENARIO A


EARTH&SPACE 2010



SCENARIO A


EARTH&SPACE 2010



SCENARIO A


EARTH&SPACE 2010



SCENARIO B

time: 0.0 s

time: 0.0 s

EARTH&SPACE 2010



SCENARIO B

time: 1.0 s

EARTH&SPACE 2010



SCENARIO B


EARTH&SPACE 2010



SCENARIO C

time: 0.0 s

time: 0.0 s

EARTH&SPACE 2010



SCENARIO C

time: 1.0 s

time: 1.0 s

EARTH&SPACE 2010



SCENARIO C

time: 3.0 s

CONCLUSIONS


CONCLUSIONS







A CASE STUDY





A CASE STUDY




SCENARIO EFFECT OF ACTION EFFECT OF DAMAGE

A

Irreversible direct damage of

impacted leg:

VULNERABLE TO ACTION

(not disproportionate, local

resistance may be increased)

Overloading of adjacent legs

and part of monopile,

but no damage propagation:

ROBUST BEHAVIOR

(other damages to be

studied)

B

Elastic deformation:

NOT VULNERABLE TO

CONSIDERED ACTION

---

C

Elastic deformation:

NOT VULNERABLE TO

CONSIDERED ACTION---

EARTH&SPACE 2010


Nonlinear dynamic investigation results

700 ton700 ton

700 ton700 ton

700 ton700 ton

700 ton700 ton

EARTH&SPACE 2010


FAILURECAUSES TYPES

ACCIDENTAL

ACTIONS

HUMAN ERRORS

§ DESIGN

§ EXECUTION

§ MAINTENANCE

§ IMPACTS

§ COLLISIONS

§ FIRES

UNFAVORABLE

COMBINATIONS

of usual load values or

circumstances:

SWISS CHEESE THEORY

BLADES

§ OVER SPEED

§ FATIGUE FAILURE

§ LOCAL BUCKLING

Handling exceptions of OWT

EARTH&SPACE 2010


FAILURECAUSES TYPES

ACCIDENTAL

ACTIONS

HUMAN ERRORS

§ DESIGN

§ EXECUTION

§ MAINTENANCE

§ IMPACTS

§ COLLISIONS

§ FIRES

UNFAVORABLE

COMBINATIONS


circumstances:

SWISS CHEESE THEORY

BLADES

§ OVER SPEED

§ FATIGUE FAILURE

§ LOCAL BUCKLING

TOWER

§ SHAFT CRACKS

§ WELDING FAILURE

(FATIGUE OR

FAULTY DESIGN)


EARTH&SPACE 2010


FAILURECAUSES TYPES

ACCIDENTAL

ACTIONS

HUMAN ERRORS

§ DESIGN

§ EXECUTION

§ MAINTENANCE

§ IMPACTS

§ COLLISIONS

§ FIRES

UNFAVORABLE

COMBINATIONS


circumstances:

SWISS CHEESE THEORY

BLADES

§ OVER SPEED

§ FATIGUE FAILURE

§ LOCAL BUCKLING

TOWER

§ SHAFT CRACKS

§ WELDING FAILURE

(FATIGUE OR

FAULTY DESIGN)

FOUNDATION

§ MOSTLY FOR OWT

IN CONSTRUCTION


EARTH&SPACE 2010


PreventionPrevention

Indirect design Direct design

Top-downmethods

Bottom-upmethods

Collapse

resistance

Structural

robustness

PresumptionPresumption

Event control

Specific Specific

analysesanalyses

StructuralStructural

measuresmeasures performedavoided

Critical Critical

eventevent modeled

no yes

Invulnerability

Unaccounted

may happen!

No hazards

can occur

Hazards don’t

cause failure

Progressive

collapse

susceptibility

?

Effects areEffects are

uncertainuncertain

?

Behavior followingBehavior following

other hazardsother hazards

remains unknown!remains unknown!

irrelevant

FAULTFAULTFAILUREFAILURE

SECURITYSECURITY INVULNERABILITYINVULNERABILITY


Structural Integrity Evaluation of Offshore Wind Turbines

Luisa Giuliani Franco Bontempi

[email protected] [email protected]

Structural and Geotechnical Engineering Department

University of Rome “La Sapienza”

10/31

1 2

S14

32 4

S1

S124

3 4

S2

3

S124

4

S3

2

1

3

4

1

2

3

4

1

4

1

3

1

2

42

3

2

4

3

42

3

2

1 1 1

4

3

42

3

d=0

d=2

d=1

d=3

2

1

3

4d=4

3

4

S123

S1234

4

S134

S13

4

S134

S23

4

S134

S12

4

S4

S0

Computational tree of a non-deterministic Turing

machine:

all possible configurations are computed in polynomial time

(# computational steps s = # system elements E).

State of acceptance: damaged

configuration

Initial state: nominal

configuration

Damaged configurationsEARTH&SPACE 2010


D I1 Di1 , D/d

r1maxI a

i

ia <<→<<∀

−

=

EARTH&SPACE 2010


Additional slides

0 1 2 3 4 5 6 d

λ

0 1 2 3 4 5 6 d

λa. Maximum inclination of all the secant linesthat connect the first point of the curveswith the points pertaining to greater damage levels.

D I1 Di1 , D/d

r1maxI a

i

ia <<→<<∀

−

=

EARTH&SPACE 2010


Additional slides

0 1 2 3 4 5 6 d

λ

0 1 2 3 4 5 6 d

λa. Maximum inclination of all the secant linesthat connect the first point of the curveswith the points pertaining to greater damage levels

b. Highest variation of secant lines between two subsequent points (critical elements are most relevant)

( ) ( )Di

2

rrrrmaxI 1iii1i

b <∀

−−−

= +−)isostatic( 5.0I0 )linear( b ≤≤←

D I1 Di1 , D/d

r1maxI a

i

ia <<→<<∀

−

=

EARTH&SPACE 2010


Additional slides

c. Area subtended by the curve of minima weighted by the difference between that area and the area subtended from the curve of maxima (representing the scattering)

a. Maximum inclination of all the secant linesthat connect the first point of the curveswith the points pertaining to greater damage levels


[ ] [ ]

−⋅+= ∑∑==

D

0d

LOWUPD

0d

LOWc )d(r)d(rk)d(rDI ( ) 1k0for,1D2I5.0 c <<−⋅<≤→

0 1 2 3 4 5 6 d

λ

0 1 2 3 4 5 6 d

λ

( ) ( )Di

2

rrrrmaxI 1iii1i

b <∀

−−−


( ) ( )Di

2

rrrrmaxI 1iii1i

b <∀

−−−


D I1 Di1 , D/d

r1maxI a

i

ia <<→<<∀

−

=

EARTH&SPACE 2010


Additional slides

0 1 2 3 4 5 6 d

λ

0 1 2 3 4 5 6 d

λ




d. Scattering from linear trend, calculated as the area subtended between the curves and the straight line that connect the point of the integer structure with that one of the null one.

[ ] [ ] 2

D)1k()d(rk )d(rI

D

0d

UPD

0d

LOWd ∑∑

==

+−+= ED and 1k0for , 1I1 d =<<<≤−→

( ) 1k0for,1D2I5.0 c <<−⋅<≤→[ ] [ ]

−⋅+= ∑∑==

D

0d

LOWUPD

0d

LOWc )d(r)d(rk)d(rDI

( ) ( )Di

2

rrrrmaxI 1iii1i

b <∀

−−−


[ ] [ ]

−⋅+= ∑∑==

D

0d

LOWUPD

0d

LOWc )d(r)d(rk)d(rDI ( ) 1k0for,1D2I5.0 c <<−⋅<≤→

[ ] [ ] 2

D)1k()d(rk )d(rI

D

0d

UPD

0d

LOWd ∑∑

==

+−+= ED and 1k0for , 1I1 d =<<<≤−→

D I1 Di1 , D/d

r1maxI a

i

ia <<→<<∀

−

=

EARTH&SPACE 2010


Additional slides




e. Upper and lower bound for maximal damage that makes the structure unstable

UPLOWe DkDI ⋅+= E2I0and1k0andDDD1 c

UPLOW ≤≤<<≤≤≤←

d. Scattering from linear trend, calculated as the area subtended between the curves and the straight line that connect the point of the integer structure with that one of the null one.

0 1 2 3 4 5 6 d

λ

0 1 2 3 4 5 6 d

λ

DLOW DUP

EARTH&SPACE 2010


Additional slides

START

d := 0

for e =1 to E

d := 1

NL static analysis λu0

λu,e1

Remove element e

Pushover analysis

Restore element e

for d = 2 to D

λu1MAX, e1

MAX

λu1MIN, e1

MIN

Remove element e(d-1)MIN

for e =1 to E

λu,ed

Remove element e

Pushover analysis

Restore element e

CALL CALL ““CURVE MAXCURVE MAX””

CALL CALL ““CURVE MINCURVE MIN””

Robustness quantification

if e <> edMIN

λudMIN,

edMIN

““CURVE MINCURVE MIN““ MACROMACRO

Curve of minima

END

Restore integer structure

Calculate area or derivativesExtrapolate equations

Calculate corresponding ∆RFix an admitted ∆d

Identify critical elementsSpot abrupt decrement

ROBUSTNESS QUANTIFICATIONROBUSTNESS QUANTIFICATION

ALGORITHM FOR HEURISTIC OPTIMIZATIONALGORITHM FOR HEURISTIC OPTIMIZATION

EARTH&SPACE 2010


Additional slides

Pushover on integer structure

Resulting robustness histogram

Plastic strain development Axial stress development

Meshed elements Plastic moment development

Response curve

Max and min robustness histogramsPlasticization development

ALGORITHM FOR REDUCED ANALYSESALGORITHM FOR REDUCED ANALYSESMax resistance

STAR STRUCTURE ROBUSTNESS

00

,51

0 1 2 3 4 5 6 7 8Damage Level

PU

[a

d]

MAX MIN

td

RR

Dd

cos25.0max,...,1

←=

∂

∂=′

=

EARTH&SPACE 2010


Additional slides

# of elements: E = 8

static indetermin. level: i = 21

lower max. damage: Dmin = 8

upper max. damage: Dmax = 8

fixed max. damage: D = 8

reduced combination: Cred = 65

exhaust. combination: Cex= 256

λλgg

1 2

4

3

5

8

6

7

STATIC INDETERMINANCY: high restrain grade

Damage

d El. ID Pumin El. ID Pumax

0 0 1 0 1

1 1 0,831745 3 0,896185

2 5 0,648331 7 0,832096

3 4 0,523591 2 0,684849

4 8 0,376882 8 0,580928

5 2 0,269581 6 0,429733

6 6 0,16434 4 0,320632

7 7 0,042504 1 0,261956

8 3 0 5 0

MIN CFG MAX CFG

Ib ≈ 0

Ia ≈ 1

ROBUSTNESS INDICATOR:

( ) ( )Di

2

rrrrmaxI 1iii1i

b <∀

−−−

= +− )isostatic( 5.0I0 )linear( b ≤≤→

Ed0 Ed

)d(rmaxI a ≤≤∀

= )isostatic( EI1 b ≤≤→

Ib maximum slope pt. tangent (measure the abrupt decrement due to the removal of critical element)

Ia maximum secant starting from the 1st pt. (account for thelateness of an abrupt decrement)

EARTH&SPACE 2010


Additional slides







exhaust. combination: Cex= 695860λ

15 16 1417

11 9 1210

18 20 1921

13

7 5 3 1 2 4 6 8

TRUSS STRUCTURE ROBUSTNESS

00

.25

0.5

0.7

51

0 1 2 3 4 5 6 7 8 9Damage Level

PU [ad] MAX MIN

EARTH&SPACE 2010


Additional slides








Damage


0 0 1 0 1

1 9 0,471351 1 0,888941

2 3 0 2 0,888941

3 10 0 11 0,628625

4 17 0 12 0,628625

5 16 0 5 0,628625

6 1 0 6 0,628625

7 5 0 13 0,628625

8 11 0 14 0,628625

9 6 0 17 0

MIN CFG MAX CFG

12

1 2

11 5 6 13 14

17

9

3

λ

15 16 1417

11 9 1210

18 20 1921

13

7 5 3 1 2 4 6 8

MAX

1

15 16 14

11 9 1210

18 20 1921

13

7 5 3 2 6 84

17

0,26 > Ib > 0,13

MIN

15 16 1417

11 9 1210

18 20 1921

13

7 5 3 1 2 4 6 8

4,76 > Ia > 1,11

EARTH&SPACE 2010


Additional slides








5

8 6 97

12 10 1311

4 2 31

λ

VIERENDEEL STRUCTURE ROBUSTNESS

00

,25

0,5

0,7

51

0 1 2 3 4 5 6 7 8 9 10Damage Level

PU [ad]MAX MIN

EARTH&SPACE 2010


Additional slides








Damage


0 0 1 0 1

1 6 0,187621 1 0,938097

2 10 0 2 0,625317

3 1 0 3 0,375242

4 2 0 6 0,187621

5 3 0 7 0,187621

6 4 0 8 0,187621

7 5 0 9 0,187621

8 7 0 4 0,187621

9 8 0 5 0,187621

10 9 0 10 0

MIN CFG MAX CFG

6

1

2

3

7 8 9 4 5 10

6

10

5

8 6 97

12 10 1311

4 2 31

λ

MIN

5

8 6 97

12 1311

4 2 31

10

0,31 > Icr > 0,09

MAX

λ

5

8 6 97

12 1311

4 2 31

10

8,12 > Ia > 2,03

TRUSS STRUCTURE ROBUSTNESS

00,2

50,5

0,7

51

0 1 2 3 4 5 6 7 8 9Damage Level

PU [ad] MAX MIN

EARTH&SPACE 2010


Additional slides

5

8 6 97

12 10 1311

4 2 31

λ

VIERENDEEL STRUCTURE ROBUSTNESS

00

,51

0 1 2 3 4 5 6 7 8 9 10Damage Level

PU [ad] MAX MIN

6

6

1

2

3

7 8 9 4 5 1010

High element connectionHigh element number

14

5 3 1 2 4 6 8

λ

7 5 3 1 2 4 6 8

14

11 9 1210

18 20 1921

13 15 1617

λ

STATIC INDETERMINANCY

i = 4 i = 12

0,26 > Ib > 0,13 0,31 > Ib > 0,099

3

12

1 2

11 5 6 13 14

17

8,12 > Ia > 2,034,76 > Ia > 1,11

EARTH&SPACE 2010


Additional slides

3

1

4 2

5 λλgg

ST

AT

IC I

ND

ET

ER

MIN

AN

CY

restr

ain

t

I3V STRUCTURE ROBUSTNESS

00

,51

0 1 2 3 4 5

Damage Level

PU

[k

N]

MAX MIN

I3C STRUCTURE ROBUSTNESS

00

,25

0,5

0,7

51

0 1 2 3 4Damage Level

PU

[k

N]

MAX MIN

3

1

2 4

λλgg

connection

14

13 15

16

10

12 11

9

6 5

1 2

7

8

4

3

λλgg

I3E STRUCTURE ROBUSTNESS

00

,25

0,5

0,7

51

0 1 2 3 4 5Damage Level

PU

[k

N]

MAX MIN

ele

me

nt

EARTH&SPACE 2010


Additional slides

HIGH CONNECTION

Continuity

Compartmentalization

Isolation

Element

numberElement

connection

LOCAL REDUCTION

OF CONTINUITY

LOCAL MECHANISM

DEVELOPMENT

Redundancy

Fragility

LOW CONNECTION

LOCAL REDUCTION OF

DUCTILITY

(inhomogeneous stiffening

of predetermined sections)

EARLY RUPTURE AND

DETACHMENT

Element

ductility

Ductility

External

(restraints)

STRESS IS NOT TRANSMITTED

COLLAPSE

STANDSTILL

STRESS REDISTRIBUTION

HIGH STRESS TRANSMISSION

on adjoining elements after a localized failure

TRIGGERING OF CHAIN

RUPTURE

PROGRESSIVE COLLAPSE

DISPROPORTIONATE COLLAPSE SUSCEPTIBILITY

SUDDEN/EARLY

COLLAPSE

Internal

(constraints)

*

Starossek &

Wolff, 2005*

FEASIBLE ALTERNATE LOAD

PATH

ROBUSTNESS

EARTH&SPACE 2010


L. Giuliani, F. Bontempi - Structural Integrity Evaluation of Offshore Wind Turbines

Why caring for structural integrity?

2

EARTH&SPACE 2010

LILLEGRUND offshore wind farm(Øresund between Malmö and København, Siemens, June 2008)

Design

3 - Structural Integrity Evaluation of Offshore Wind Turbines - Giuliani